libstdc++
type_traits
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1 // C++11 <type_traits> -*- C++ -*-
2 
3 // Copyright (C) 2007-2024 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 include/type_traits
26  * This is a Standard C++ Library header.
27  */
28 
29 #ifndef _GLIBCXX_TYPE_TRAITS
30 #define _GLIBCXX_TYPE_TRAITS 1
31 
32 #pragma GCC system_header
33 
34 #if __cplusplus < 201103L
35 # include <bits/c++0x_warning.h>
36 #else
37 
38 #include <bits/c++config.h>
39 
40 #define __glibcxx_want_bool_constant
41 #define __glibcxx_want_bounded_array_traits
42 #define __glibcxx_want_has_unique_object_representations
43 #define __glibcxx_want_integral_constant_callable
44 #define __glibcxx_want_is_aggregate
45 #define __glibcxx_want_is_constant_evaluated
46 #define __glibcxx_want_is_final
47 #define __glibcxx_want_is_invocable
48 #define __glibcxx_want_is_layout_compatible
49 #define __glibcxx_want_is_nothrow_convertible
50 #define __glibcxx_want_is_null_pointer
51 #define __glibcxx_want_is_pointer_interconvertible
52 #define __glibcxx_want_is_scoped_enum
53 #define __glibcxx_want_is_swappable
54 #define __glibcxx_want_logical_traits
55 #define __glibcxx_want_reference_from_temporary
56 #define __glibcxx_want_remove_cvref
57 #define __glibcxx_want_result_of_sfinae
58 #define __glibcxx_want_transformation_trait_aliases
59 #define __glibcxx_want_type_identity
60 #define __glibcxx_want_type_trait_variable_templates
61 #define __glibcxx_want_unwrap_ref
62 #define __glibcxx_want_void_t
63 #include <bits/version.h>
64 
65 namespace std _GLIBCXX_VISIBILITY(default)
66 {
67 _GLIBCXX_BEGIN_NAMESPACE_VERSION
68 
69  template<typename _Tp>
70  class reference_wrapper;
71 
72  /**
73  * @defgroup metaprogramming Metaprogramming
74  * @ingroup utilities
75  *
76  * Template utilities for compile-time introspection and modification,
77  * including type classification traits, type property inspection traits
78  * and type transformation traits.
79  *
80  * @since C++11
81  *
82  * @{
83  */
84 
85  /// integral_constant
86  template<typename _Tp, _Tp __v>
87  struct integral_constant
88  {
89  static constexpr _Tp value = __v;
90  using value_type = _Tp;
91  using type = integral_constant<_Tp, __v>;
92  constexpr operator value_type() const noexcept { return value; }
93 
94 #ifdef __cpp_lib_integral_constant_callable // C++ >= 14
95  constexpr value_type operator()() const noexcept { return value; }
96 #endif
97  };
98 
99 #if ! __cpp_inline_variables
100  template<typename _Tp, _Tp __v>
101  constexpr _Tp integral_constant<_Tp, __v>::value;
102 #endif
103 
104  /// @cond undocumented
105  /// bool_constant for C++11
106  template<bool __v>
107  using __bool_constant = integral_constant<bool, __v>;
108  /// @endcond
109 
110  /// The type used as a compile-time boolean with true value.
111  using true_type = __bool_constant<true>;
112 
113  /// The type used as a compile-time boolean with false value.
114  using false_type = __bool_constant<false>;
115 
116 #ifdef __cpp_lib_bool_constant // C++ >= 17
117  /// Alias template for compile-time boolean constant types.
118  /// @since C++17
119  template<bool __v>
120  using bool_constant = __bool_constant<__v>;
121 #endif
122 
123  // Metaprogramming helper types.
124 
125  // Primary template.
126  /// Define a member typedef `type` only if a boolean constant is true.
127  template<bool, typename _Tp = void>
128  struct enable_if
129  { };
130 
131  // Partial specialization for true.
132  template<typename _Tp>
133  struct enable_if<true, _Tp>
134  { using type = _Tp; };
135 
136  // __enable_if_t (std::enable_if_t for C++11)
137  template<bool _Cond, typename _Tp = void>
138  using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
139 
140  template<bool>
141  struct __conditional
142  {
143  template<typename _Tp, typename>
144  using type = _Tp;
145  };
146 
147  template<>
148  struct __conditional<false>
149  {
150  template<typename, typename _Up>
151  using type = _Up;
152  };
153 
154  // More efficient version of std::conditional_t for internal use (and C++11)
155  template<bool _Cond, typename _If, typename _Else>
156  using __conditional_t
157  = typename __conditional<_Cond>::template type<_If, _Else>;
158 
159  /// @cond undocumented
160  template <typename _Type>
161  struct __type_identity
162  { using type = _Type; };
163 
164  template<typename _Tp>
165  using __type_identity_t = typename __type_identity<_Tp>::type;
166 
167  namespace __detail
168  {
169  // A variadic alias template that resolves to its first argument.
170  template<typename _Tp, typename...>
171  using __first_t = _Tp;
172 
173  // These are deliberately not defined.
174  template<typename... _Bn>
175  auto __or_fn(int) -> __first_t<false_type,
176  __enable_if_t<!bool(_Bn::value)>...>;
177 
178  template<typename... _Bn>
179  auto __or_fn(...) -> true_type;
180 
181  template<typename... _Bn>
182  auto __and_fn(int) -> __first_t<true_type,
183  __enable_if_t<bool(_Bn::value)>...>;
184 
185  template<typename... _Bn>
186  auto __and_fn(...) -> false_type;
187  } // namespace detail
188 
189  // Like C++17 std::dis/conjunction, but usable in C++11 and resolves
190  // to either true_type or false_type which allows for a more efficient
191  // implementation that avoids recursive class template instantiation.
192  template<typename... _Bn>
193  struct __or_
194  : decltype(__detail::__or_fn<_Bn...>(0))
195  { };
196 
197  template<typename... _Bn>
198  struct __and_
199  : decltype(__detail::__and_fn<_Bn...>(0))
200  { };
201 
202  template<typename _Pp>
203  struct __not_
204  : __bool_constant<!bool(_Pp::value)>
205  { };
206  /// @endcond
207 
208 #ifdef __cpp_lib_logical_traits // C++ >= 17
209 
210  /// @cond undocumented
211  template<typename... _Bn>
212  inline constexpr bool __or_v = __or_<_Bn...>::value;
213  template<typename... _Bn>
214  inline constexpr bool __and_v = __and_<_Bn...>::value;
215 
216  namespace __detail
217  {
218  template<typename /* = void */, typename _B1, typename... _Bn>
219  struct __disjunction_impl
220  { using type = _B1; };
221 
222  template<typename _B1, typename _B2, typename... _Bn>
223  struct __disjunction_impl<__enable_if_t<!bool(_B1::value)>, _B1, _B2, _Bn...>
224  { using type = typename __disjunction_impl<void, _B2, _Bn...>::type; };
225 
226  template<typename /* = void */, typename _B1, typename... _Bn>
227  struct __conjunction_impl
228  { using type = _B1; };
229 
230  template<typename _B1, typename _B2, typename... _Bn>
231  struct __conjunction_impl<__enable_if_t<bool(_B1::value)>, _B1, _B2, _Bn...>
232  { using type = typename __conjunction_impl<void, _B2, _Bn...>::type; };
233  } // namespace __detail
234  /// @endcond
235 
236  template<typename... _Bn>
237  struct conjunction
238  : __detail::__conjunction_impl<void, _Bn...>::type
239  { };
240 
241  template<>
242  struct conjunction<>
243  : true_type
244  { };
245 
246  template<typename... _Bn>
247  struct disjunction
248  : __detail::__disjunction_impl<void, _Bn...>::type
249  { };
250 
251  template<>
252  struct disjunction<>
253  : false_type
254  { };
255 
256  template<typename _Pp>
257  struct negation
258  : __not_<_Pp>::type
259  { };
260 
261  /** @ingroup variable_templates
262  * @{
263  */
264  template<typename... _Bn>
265  inline constexpr bool conjunction_v = conjunction<_Bn...>::value;
266 
267  template<typename... _Bn>
268  inline constexpr bool disjunction_v = disjunction<_Bn...>::value;
269 
270  template<typename _Pp>
271  inline constexpr bool negation_v = negation<_Pp>::value;
272  /// @}
273 
274 #endif // __cpp_lib_logical_traits
275 
276  // Forward declarations
277  template<typename>
278  struct is_reference;
279  template<typename>
280  struct is_function;
281  template<typename>
282  struct is_void;
283  template<typename>
284  struct remove_cv;
285  template<typename>
286  struct is_const;
287 
288  /// @cond undocumented
289  template<typename>
290  struct __is_array_unknown_bounds;
291 
292  // Helper functions that return false_type for incomplete classes,
293  // incomplete unions and arrays of known bound from those.
294 
295  template <typename _Tp, size_t = sizeof(_Tp)>
296  constexpr true_type __is_complete_or_unbounded(__type_identity<_Tp>)
297  { return {}; }
298 
299  template <typename _TypeIdentity,
300  typename _NestedType = typename _TypeIdentity::type>
301  constexpr typename __or_<
302  is_reference<_NestedType>,
303  is_function<_NestedType>,
304  is_void<_NestedType>,
305  __is_array_unknown_bounds<_NestedType>
306  >::type __is_complete_or_unbounded(_TypeIdentity)
307  { return {}; }
308 
309  // __remove_cv_t (std::remove_cv_t for C++11).
310  template<typename _Tp>
311  using __remove_cv_t = typename remove_cv<_Tp>::type;
312  /// @endcond
313 
314  // Primary type categories.
315 
316  /// is_void
317  template<typename _Tp>
318  struct is_void
319  : public false_type { };
320 
321  template<>
322  struct is_void<void>
323  : public true_type { };
324 
325  template<>
326  struct is_void<const void>
327  : public true_type { };
328 
329  template<>
330  struct is_void<volatile void>
331  : public true_type { };
332 
333  template<>
334  struct is_void<const volatile void>
335  : public true_type { };
336 
337  /// @cond undocumented
338  template<typename>
339  struct __is_integral_helper
340  : public false_type { };
341 
342  template<>
343  struct __is_integral_helper<bool>
344  : public true_type { };
345 
346  template<>
347  struct __is_integral_helper<char>
348  : public true_type { };
349 
350  template<>
351  struct __is_integral_helper<signed char>
352  : public true_type { };
353 
354  template<>
355  struct __is_integral_helper<unsigned char>
356  : public true_type { };
357 
358  // We want is_integral<wchar_t> to be true (and make_signed/unsigned to work)
359  // even when libc doesn't provide working <wchar.h> and related functions,
360  // so don't check _GLIBCXX_USE_WCHAR_T here.
361  template<>
362  struct __is_integral_helper<wchar_t>
363  : public true_type { };
364 
365 #ifdef _GLIBCXX_USE_CHAR8_T
366  template<>
367  struct __is_integral_helper<char8_t>
368  : public true_type { };
369 #endif
370 
371  template<>
372  struct __is_integral_helper<char16_t>
373  : public true_type { };
374 
375  template<>
376  struct __is_integral_helper<char32_t>
377  : public true_type { };
378 
379  template<>
380  struct __is_integral_helper<short>
381  : public true_type { };
382 
383  template<>
384  struct __is_integral_helper<unsigned short>
385  : public true_type { };
386 
387  template<>
388  struct __is_integral_helper<int>
389  : public true_type { };
390 
391  template<>
392  struct __is_integral_helper<unsigned int>
393  : public true_type { };
394 
395  template<>
396  struct __is_integral_helper<long>
397  : public true_type { };
398 
399  template<>
400  struct __is_integral_helper<unsigned long>
401  : public true_type { };
402 
403  template<>
404  struct __is_integral_helper<long long>
405  : public true_type { };
406 
407  template<>
408  struct __is_integral_helper<unsigned long long>
409  : public true_type { };
410 
411  // Conditionalizing on __STRICT_ANSI__ here will break any port that
412  // uses one of these types for size_t.
413 #if defined(__GLIBCXX_TYPE_INT_N_0)
414  __extension__
415  template<>
416  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_0>
417  : public true_type { };
418 
419  __extension__
420  template<>
421  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_0>
422  : public true_type { };
423 #endif
424 #if defined(__GLIBCXX_TYPE_INT_N_1)
425  __extension__
426  template<>
427  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_1>
428  : public true_type { };
429 
430  __extension__
431  template<>
432  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_1>
433  : public true_type { };
434 #endif
435 #if defined(__GLIBCXX_TYPE_INT_N_2)
436  __extension__
437  template<>
438  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_2>
439  : public true_type { };
440 
441  __extension__
442  template<>
443  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_2>
444  : public true_type { };
445 #endif
446 #if defined(__GLIBCXX_TYPE_INT_N_3)
447  __extension__
448  template<>
449  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_3>
450  : public true_type { };
451 
452  __extension__
453  template<>
454  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_3>
455  : public true_type { };
456 #endif
457  /// @endcond
458 
459  /// is_integral
460  template<typename _Tp>
461  struct is_integral
462  : public __is_integral_helper<__remove_cv_t<_Tp>>::type
463  { };
464 
465  /// @cond undocumented
466  template<typename>
467  struct __is_floating_point_helper
468  : public false_type { };
469 
470  template<>
471  struct __is_floating_point_helper<float>
472  : public true_type { };
473 
474  template<>
475  struct __is_floating_point_helper<double>
476  : public true_type { };
477 
478  template<>
479  struct __is_floating_point_helper<long double>
480  : public true_type { };
481 
482 #ifdef __STDCPP_FLOAT16_T__
483  template<>
484  struct __is_floating_point_helper<_Float16>
485  : public true_type { };
486 #endif
487 
488 #ifdef __STDCPP_FLOAT32_T__
489  template<>
490  struct __is_floating_point_helper<_Float32>
491  : public true_type { };
492 #endif
493 
494 #ifdef __STDCPP_FLOAT64_T__
495  template<>
496  struct __is_floating_point_helper<_Float64>
497  : public true_type { };
498 #endif
499 
500 #ifdef __STDCPP_FLOAT128_T__
501  template<>
502  struct __is_floating_point_helper<_Float128>
503  : public true_type { };
504 #endif
505 
506 #ifdef __STDCPP_BFLOAT16_T__
507  template<>
508  struct __is_floating_point_helper<__gnu_cxx::__bfloat16_t>
509  : public true_type { };
510 #endif
511 
512 #if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
513  template<>
514  struct __is_floating_point_helper<__float128>
515  : public true_type { };
516 #endif
517  /// @endcond
518 
519  /// is_floating_point
520  template<typename _Tp>
521  struct is_floating_point
522  : public __is_floating_point_helper<__remove_cv_t<_Tp>>::type
523  { };
524 
525  /// is_array
526 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_array)
527  template<typename _Tp>
528  struct is_array
529  : public __bool_constant<__is_array(_Tp)>
530  { };
531 #else
532  template<typename>
533  struct is_array
534  : public false_type { };
535 
536  template<typename _Tp, std::size_t _Size>
537  struct is_array<_Tp[_Size]>
538  : public true_type { };
539 
540  template<typename _Tp>
541  struct is_array<_Tp[]>
542  : public true_type { };
543 #endif
544 
545  template<typename>
546  struct __is_pointer_helper
547  : public false_type { };
548 
549  template<typename _Tp>
550  struct __is_pointer_helper<_Tp*>
551  : public true_type { };
552 
553  /// is_pointer
554  template<typename _Tp>
555  struct is_pointer
556  : public __is_pointer_helper<__remove_cv_t<_Tp>>::type
557  { };
558 
559  /// is_lvalue_reference
560  template<typename>
561  struct is_lvalue_reference
562  : public false_type { };
563 
564  template<typename _Tp>
565  struct is_lvalue_reference<_Tp&>
566  : public true_type { };
567 
568  /// is_rvalue_reference
569  template<typename>
570  struct is_rvalue_reference
571  : public false_type { };
572 
573  template<typename _Tp>
574  struct is_rvalue_reference<_Tp&&>
575  : public true_type { };
576 
577  /// is_member_object_pointer
578 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_object_pointer)
579  template<typename _Tp>
580  struct is_member_object_pointer
581  : public __bool_constant<__is_member_object_pointer(_Tp)>
582  { };
583 #else
584  template<typename>
585  struct __is_member_object_pointer_helper
586  : public false_type { };
587 
588  template<typename _Tp, typename _Cp>
589  struct __is_member_object_pointer_helper<_Tp _Cp::*>
590  : public __not_<is_function<_Tp>>::type { };
591 
592 
593  template<typename _Tp>
594  struct is_member_object_pointer
595  : public __is_member_object_pointer_helper<__remove_cv_t<_Tp>>::type
596  { };
597 #endif
598 
599 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_function_pointer)
600  /// is_member_function_pointer
601  template<typename _Tp>
602  struct is_member_function_pointer
603  : public __bool_constant<__is_member_function_pointer(_Tp)>
604  { };
605 #else
606  template<typename>
607  struct __is_member_function_pointer_helper
608  : public false_type { };
609 
610  template<typename _Tp, typename _Cp>
611  struct __is_member_function_pointer_helper<_Tp _Cp::*>
612  : public is_function<_Tp>::type { };
613 
614  /// is_member_function_pointer
615  template<typename _Tp>
616  struct is_member_function_pointer
617  : public __is_member_function_pointer_helper<__remove_cv_t<_Tp>>::type
618  { };
619 #endif
620 
621  /// is_enum
622  template<typename _Tp>
623  struct is_enum
624  : public __bool_constant<__is_enum(_Tp)>
625  { };
626 
627  /// is_union
628  template<typename _Tp>
629  struct is_union
630  : public __bool_constant<__is_union(_Tp)>
631  { };
632 
633  /// is_class
634  template<typename _Tp>
635  struct is_class
636  : public __bool_constant<__is_class(_Tp)>
637  { };
638 
639  /// is_function
640 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function)
641  template<typename _Tp>
642  struct is_function
643  : public __bool_constant<__is_function(_Tp)>
644  { };
645 #else
646  template<typename _Tp>
647  struct is_function
648  : public __bool_constant<!is_const<const _Tp>::value> { };
649 
650  template<typename _Tp>
651  struct is_function<_Tp&>
652  : public false_type { };
653 
654  template<typename _Tp>
655  struct is_function<_Tp&&>
656  : public false_type { };
657 #endif
658 
659 #ifdef __cpp_lib_is_null_pointer // C++ >= 11
660  /// is_null_pointer (LWG 2247).
661  template<typename _Tp>
662  struct is_null_pointer
663  : public false_type { };
664 
665  template<>
666  struct is_null_pointer<std::nullptr_t>
667  : public true_type { };
668 
669  template<>
670  struct is_null_pointer<const std::nullptr_t>
671  : public true_type { };
672 
673  template<>
674  struct is_null_pointer<volatile std::nullptr_t>
675  : public true_type { };
676 
677  template<>
678  struct is_null_pointer<const volatile std::nullptr_t>
679  : public true_type { };
680 
681  /// __is_nullptr_t (deprecated extension).
682  /// @deprecated Non-standard. Use `is_null_pointer` instead.
683  template<typename _Tp>
684  struct __is_nullptr_t
685  : public is_null_pointer<_Tp>
686  { } _GLIBCXX_DEPRECATED_SUGGEST("std::is_null_pointer");
687 #endif // __cpp_lib_is_null_pointer
688 
689  // Composite type categories.
690 
691  /// is_reference
692 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_reference)
693  template<typename _Tp>
694  struct is_reference
695  : public __bool_constant<__is_reference(_Tp)>
696  { };
697 #else
698  template<typename _Tp>
699  struct is_reference
700  : public false_type
701  { };
702 
703  template<typename _Tp>
704  struct is_reference<_Tp&>
705  : public true_type
706  { };
707 
708  template<typename _Tp>
709  struct is_reference<_Tp&&>
710  : public true_type
711  { };
712 #endif
713 
714  /// is_arithmetic
715  template<typename _Tp>
716  struct is_arithmetic
717  : public __or_<is_integral<_Tp>, is_floating_point<_Tp>>::type
718  { };
719 
720  /// is_fundamental
721  template<typename _Tp>
722  struct is_fundamental
723  : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
724  is_null_pointer<_Tp>>::type
725  { };
726 
727  /// is_object
728 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_object)
729  template<typename _Tp>
730  struct is_object
731  : public __bool_constant<__is_object(_Tp)>
732  { };
733 #else
734  template<typename _Tp>
735  struct is_object
736  : public __not_<__or_<is_function<_Tp>, is_reference<_Tp>,
737  is_void<_Tp>>>::type
738  { };
739 #endif
740 
741  template<typename>
742  struct is_member_pointer;
743 
744  /// is_scalar
745  template<typename _Tp>
746  struct is_scalar
747  : public __or_<is_arithmetic<_Tp>, is_enum<_Tp>, is_pointer<_Tp>,
748  is_member_pointer<_Tp>, is_null_pointer<_Tp>>::type
749  { };
750 
751  /// is_compound
752  template<typename _Tp>
753  struct is_compound
754  : public __bool_constant<!is_fundamental<_Tp>::value> { };
755 
756  /// is_member_pointer
757 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_pointer)
758  template<typename _Tp>
759  struct is_member_pointer
760  : public __bool_constant<__is_member_pointer(_Tp)>
761  { };
762 #else
763  /// @cond undocumented
764  template<typename _Tp>
765  struct __is_member_pointer_helper
766  : public false_type { };
767 
768  template<typename _Tp, typename _Cp>
769  struct __is_member_pointer_helper<_Tp _Cp::*>
770  : public true_type { };
771  /// @endcond
772 
773  template<typename _Tp>
774  struct is_member_pointer
775  : public __is_member_pointer_helper<__remove_cv_t<_Tp>>::type
776  { };
777 #endif
778 
779  template<typename, typename>
780  struct is_same;
781 
782  /// @cond undocumented
783  template<typename _Tp, typename... _Types>
784  using __is_one_of = __or_<is_same<_Tp, _Types>...>;
785 
786  // Check if a type is one of the signed integer types.
787  __extension__
788  template<typename _Tp>
789  using __is_signed_integer = __is_one_of<__remove_cv_t<_Tp>,
790  signed char, signed short, signed int, signed long,
791  signed long long
792 #if defined(__GLIBCXX_TYPE_INT_N_0)
793  , signed __GLIBCXX_TYPE_INT_N_0
794 #endif
795 #if defined(__GLIBCXX_TYPE_INT_N_1)
796  , signed __GLIBCXX_TYPE_INT_N_1
797 #endif
798 #if defined(__GLIBCXX_TYPE_INT_N_2)
799  , signed __GLIBCXX_TYPE_INT_N_2
800 #endif
801 #if defined(__GLIBCXX_TYPE_INT_N_3)
802  , signed __GLIBCXX_TYPE_INT_N_3
803 #endif
804  >;
805 
806  // Check if a type is one of the unsigned integer types.
807  __extension__
808  template<typename _Tp>
809  using __is_unsigned_integer = __is_one_of<__remove_cv_t<_Tp>,
810  unsigned char, unsigned short, unsigned int, unsigned long,
811  unsigned long long
812 #if defined(__GLIBCXX_TYPE_INT_N_0)
813  , unsigned __GLIBCXX_TYPE_INT_N_0
814 #endif
815 #if defined(__GLIBCXX_TYPE_INT_N_1)
816  , unsigned __GLIBCXX_TYPE_INT_N_1
817 #endif
818 #if defined(__GLIBCXX_TYPE_INT_N_2)
819  , unsigned __GLIBCXX_TYPE_INT_N_2
820 #endif
821 #if defined(__GLIBCXX_TYPE_INT_N_3)
822  , unsigned __GLIBCXX_TYPE_INT_N_3
823 #endif
824  >;
825 
826  // Check if a type is one of the signed or unsigned integer types.
827  template<typename _Tp>
828  using __is_standard_integer
829  = __or_<__is_signed_integer<_Tp>, __is_unsigned_integer<_Tp>>;
830 
831  // __void_t (std::void_t for C++11)
832  template<typename...> using __void_t = void;
833  /// @endcond
834 
835  // Type properties.
836 
837  /// is_const
838  template<typename>
839  struct is_const
840  : public false_type { };
841 
842  template<typename _Tp>
843  struct is_const<_Tp const>
844  : public true_type { };
845 
846  /// is_volatile
847  template<typename>
848  struct is_volatile
849  : public false_type { };
850 
851  template<typename _Tp>
852  struct is_volatile<_Tp volatile>
853  : public true_type { };
854 
855  /// is_trivial
856  template<typename _Tp>
857  struct is_trivial
858  : public __bool_constant<__is_trivial(_Tp)>
859  {
860  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
861  "template argument must be a complete class or an unbounded array");
862  };
863 
864  /// is_trivially_copyable
865  template<typename _Tp>
866  struct is_trivially_copyable
867  : public __bool_constant<__is_trivially_copyable(_Tp)>
868  {
869  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
870  "template argument must be a complete class or an unbounded array");
871  };
872 
873  /// is_standard_layout
874  template<typename _Tp>
875  struct is_standard_layout
876  : public __bool_constant<__is_standard_layout(_Tp)>
877  {
878  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
879  "template argument must be a complete class or an unbounded array");
880  };
881 
882  /** is_pod
883  * @deprecated Deprecated in C++20.
884  * Use `is_standard_layout && is_trivial` instead.
885  */
886  // Could use is_standard_layout && is_trivial instead of the builtin.
887  template<typename _Tp>
888  struct
889  _GLIBCXX20_DEPRECATED_SUGGEST("is_standard_layout && is_trivial")
890  is_pod
891  : public __bool_constant<__is_pod(_Tp)>
892  {
893  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
894  "template argument must be a complete class or an unbounded array");
895  };
896 
897  /** is_literal_type
898  * @deprecated Deprecated in C++17, removed in C++20.
899  * The idea of a literal type isn't useful.
900  */
901  template<typename _Tp>
902  struct
903  _GLIBCXX17_DEPRECATED
904  is_literal_type
905  : public __bool_constant<__is_literal_type(_Tp)>
906  {
907  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
908  "template argument must be a complete class or an unbounded array");
909  };
910 
911  /// is_empty
912  template<typename _Tp>
913  struct is_empty
914  : public __bool_constant<__is_empty(_Tp)>
915  { };
916 
917  /// is_polymorphic
918  template<typename _Tp>
919  struct is_polymorphic
920  : public __bool_constant<__is_polymorphic(_Tp)>
921  { };
922 
923 #ifdef __cpp_lib_is_final // C++ >= 14
924  /// is_final
925  /// @since C++14
926  template<typename _Tp>
927  struct is_final
928  : public __bool_constant<__is_final(_Tp)>
929  { };
930 #endif
931 
932  /// is_abstract
933  template<typename _Tp>
934  struct is_abstract
935  : public __bool_constant<__is_abstract(_Tp)>
936  { };
937 
938  /// @cond undocumented
939  template<typename _Tp,
940  bool = is_arithmetic<_Tp>::value>
941  struct __is_signed_helper
942  : public false_type { };
943 
944  template<typename _Tp>
945  struct __is_signed_helper<_Tp, true>
946  : public __bool_constant<_Tp(-1) < _Tp(0)>
947  { };
948  /// @endcond
949 
950  /// is_signed
951  template<typename _Tp>
952  struct is_signed
953  : public __is_signed_helper<_Tp>::type
954  { };
955 
956  /// is_unsigned
957  template<typename _Tp>
958  struct is_unsigned
959  : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>>::type
960  { };
961 
962  /// @cond undocumented
963  template<typename _Tp, typename _Up = _Tp&&>
964  _Up
965  __declval(int);
966 
967  template<typename _Tp>
968  _Tp
969  __declval(long);
970  /// @endcond
971 
972  template<typename _Tp>
973  auto declval() noexcept -> decltype(__declval<_Tp>(0));
974 
975  template<typename>
976  struct remove_all_extents;
977 
978  /// @cond undocumented
979  template<typename _Tp>
980  struct __is_array_known_bounds
981  : public false_type
982  { };
983 
984  template<typename _Tp, size_t _Size>
985  struct __is_array_known_bounds<_Tp[_Size]>
986  : public true_type
987  { };
988 
989  template<typename _Tp>
990  struct __is_array_unknown_bounds
991  : public false_type
992  { };
993 
994  template<typename _Tp>
995  struct __is_array_unknown_bounds<_Tp[]>
996  : public true_type
997  { };
998 
999  // Destructible and constructible type properties.
1000 
1001  // In N3290 is_destructible does not say anything about function
1002  // types and abstract types, see LWG 2049. This implementation
1003  // describes function types as non-destructible and all complete
1004  // object types as destructible, iff the explicit destructor
1005  // call expression is wellformed.
1006  struct __do_is_destructible_impl
1007  {
1008  template<typename _Tp, typename = decltype(declval<_Tp&>().~_Tp())>
1009  static true_type __test(int);
1010 
1011  template<typename>
1012  static false_type __test(...);
1013  };
1014 
1015  template<typename _Tp>
1016  struct __is_destructible_impl
1017  : public __do_is_destructible_impl
1018  {
1019  using type = decltype(__test<_Tp>(0));
1020  };
1021 
1022  template<typename _Tp,
1023  bool = __or_<is_void<_Tp>,
1024  __is_array_unknown_bounds<_Tp>,
1025  is_function<_Tp>>::value,
1026  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
1027  struct __is_destructible_safe;
1028 
1029  template<typename _Tp>
1030  struct __is_destructible_safe<_Tp, false, false>
1031  : public __is_destructible_impl<typename
1032  remove_all_extents<_Tp>::type>::type
1033  { };
1034 
1035  template<typename _Tp>
1036  struct __is_destructible_safe<_Tp, true, false>
1037  : public false_type { };
1038 
1039  template<typename _Tp>
1040  struct __is_destructible_safe<_Tp, false, true>
1041  : public true_type { };
1042  /// @endcond
1043 
1044  /// is_destructible
1045  template<typename _Tp>
1046  struct is_destructible
1047  : public __is_destructible_safe<_Tp>::type
1048  {
1049  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1050  "template argument must be a complete class or an unbounded array");
1051  };
1052 
1053  /// @cond undocumented
1054 
1055  // is_nothrow_destructible requires that is_destructible is
1056  // satisfied as well. We realize that by mimicing the
1057  // implementation of is_destructible but refer to noexcept(expr)
1058  // instead of decltype(expr).
1059  struct __do_is_nt_destructible_impl
1060  {
1061  template<typename _Tp>
1062  static __bool_constant<noexcept(declval<_Tp&>().~_Tp())>
1063  __test(int);
1064 
1065  template<typename>
1066  static false_type __test(...);
1067  };
1068 
1069  template<typename _Tp>
1070  struct __is_nt_destructible_impl
1071  : public __do_is_nt_destructible_impl
1072  {
1073  using type = decltype(__test<_Tp>(0));
1074  };
1075 
1076  template<typename _Tp,
1077  bool = __or_<is_void<_Tp>,
1078  __is_array_unknown_bounds<_Tp>,
1079  is_function<_Tp>>::value,
1080  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
1081  struct __is_nt_destructible_safe;
1082 
1083  template<typename _Tp>
1084  struct __is_nt_destructible_safe<_Tp, false, false>
1085  : public __is_nt_destructible_impl<typename
1086  remove_all_extents<_Tp>::type>::type
1087  { };
1088 
1089  template<typename _Tp>
1090  struct __is_nt_destructible_safe<_Tp, true, false>
1091  : public false_type { };
1092 
1093  template<typename _Tp>
1094  struct __is_nt_destructible_safe<_Tp, false, true>
1095  : public true_type { };
1096  /// @endcond
1097 
1098  /// is_nothrow_destructible
1099  template<typename _Tp>
1100  struct is_nothrow_destructible
1101  : public __is_nt_destructible_safe<_Tp>::type
1102  {
1103  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1104  "template argument must be a complete class or an unbounded array");
1105  };
1106 
1107  /// @cond undocumented
1108  template<typename _Tp, typename... _Args>
1109  using __is_constructible_impl
1110  = __bool_constant<__is_constructible(_Tp, _Args...)>;
1111  /// @endcond
1112 
1113  /// is_constructible
1114  template<typename _Tp, typename... _Args>
1115  struct is_constructible
1116  : public __is_constructible_impl<_Tp, _Args...>
1117  {
1118  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1119  "template argument must be a complete class or an unbounded array");
1120  };
1121 
1122  /// is_default_constructible
1123  template<typename _Tp>
1124  struct is_default_constructible
1125  : public __is_constructible_impl<_Tp>
1126  {
1127  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1128  "template argument must be a complete class or an unbounded array");
1129  };
1130 
1131  /// @cond undocumented
1132  template<typename _Tp, typename = void>
1133  struct __add_lvalue_reference_helper
1134  { using type = _Tp; };
1135 
1136  template<typename _Tp>
1137  struct __add_lvalue_reference_helper<_Tp, __void_t<_Tp&>>
1138  { using type = _Tp&; };
1139 
1140  template<typename _Tp>
1141  using __add_lval_ref_t = typename __add_lvalue_reference_helper<_Tp>::type;
1142  /// @endcond
1143 
1144  /// is_copy_constructible
1145  template<typename _Tp>
1146  struct is_copy_constructible
1147  : public __is_constructible_impl<_Tp, __add_lval_ref_t<const _Tp>>
1148  {
1149  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1150  "template argument must be a complete class or an unbounded array");
1151  };
1152 
1153  /// @cond undocumented
1154  template<typename _Tp, typename = void>
1155  struct __add_rvalue_reference_helper
1156  { using type = _Tp; };
1157 
1158  template<typename _Tp>
1159  struct __add_rvalue_reference_helper<_Tp, __void_t<_Tp&&>>
1160  { using type = _Tp&&; };
1161 
1162  template<typename _Tp>
1163  using __add_rval_ref_t = typename __add_rvalue_reference_helper<_Tp>::type;
1164  /// @endcond
1165 
1166  /// is_move_constructible
1167  template<typename _Tp>
1168  struct is_move_constructible
1169  : public __is_constructible_impl<_Tp, __add_rval_ref_t<_Tp>>
1170  {
1171  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1172  "template argument must be a complete class or an unbounded array");
1173  };
1174 
1175  /// @cond undocumented
1176  template<typename _Tp, typename... _Args>
1177  using __is_nothrow_constructible_impl
1178  = __bool_constant<__is_nothrow_constructible(_Tp, _Args...)>;
1179  /// @endcond
1180 
1181  /// is_nothrow_constructible
1182  template<typename _Tp, typename... _Args>
1183  struct is_nothrow_constructible
1184  : public __is_nothrow_constructible_impl<_Tp, _Args...>
1185  {
1186  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1187  "template argument must be a complete class or an unbounded array");
1188  };
1189 
1190  /// is_nothrow_default_constructible
1191  template<typename _Tp>
1192  struct is_nothrow_default_constructible
1193  : public __is_nothrow_constructible_impl<_Tp>
1194  {
1195  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1196  "template argument must be a complete class or an unbounded array");
1197  };
1198 
1199  /// is_nothrow_copy_constructible
1200  template<typename _Tp>
1201  struct is_nothrow_copy_constructible
1202  : public __is_nothrow_constructible_impl<_Tp, __add_lval_ref_t<const _Tp>>
1203  {
1204  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1205  "template argument must be a complete class or an unbounded array");
1206  };
1207 
1208  /// is_nothrow_move_constructible
1209  template<typename _Tp>
1210  struct is_nothrow_move_constructible
1211  : public __is_nothrow_constructible_impl<_Tp, __add_rval_ref_t<_Tp>>
1212  {
1213  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1214  "template argument must be a complete class or an unbounded array");
1215  };
1216 
1217  /// @cond undocumented
1218  template<typename _Tp, typename _Up>
1219  using __is_assignable_impl = __bool_constant<__is_assignable(_Tp, _Up)>;
1220  /// @endcond
1221 
1222  /// is_assignable
1223  template<typename _Tp, typename _Up>
1224  struct is_assignable
1225  : public __is_assignable_impl<_Tp, _Up>
1226  {
1227  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1228  "template argument must be a complete class or an unbounded array");
1229  };
1230 
1231  /// is_copy_assignable
1232  template<typename _Tp>
1233  struct is_copy_assignable
1234  : public __is_assignable_impl<__add_lval_ref_t<_Tp>,
1235  __add_lval_ref_t<const _Tp>>
1236  {
1237  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1238  "template argument must be a complete class or an unbounded array");
1239  };
1240 
1241  /// is_move_assignable
1242  template<typename _Tp>
1243  struct is_move_assignable
1244  : public __is_assignable_impl<__add_lval_ref_t<_Tp>, __add_rval_ref_t<_Tp>>
1245  {
1246  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1247  "template argument must be a complete class or an unbounded array");
1248  };
1249 
1250  /// @cond undocumented
1251  template<typename _Tp, typename _Up>
1252  using __is_nothrow_assignable_impl
1253  = __bool_constant<__is_nothrow_assignable(_Tp, _Up)>;
1254  /// @endcond
1255 
1256  /// is_nothrow_assignable
1257  template<typename _Tp, typename _Up>
1258  struct is_nothrow_assignable
1259  : public __is_nothrow_assignable_impl<_Tp, _Up>
1260  {
1261  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1262  "template argument must be a complete class or an unbounded array");
1263  };
1264 
1265  /// is_nothrow_copy_assignable
1266  template<typename _Tp>
1267  struct is_nothrow_copy_assignable
1268  : public __is_nothrow_assignable_impl<__add_lval_ref_t<_Tp>,
1269  __add_lval_ref_t<const _Tp>>
1270  {
1271  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1272  "template argument must be a complete class or an unbounded array");
1273  };
1274 
1275  /// is_nothrow_move_assignable
1276  template<typename _Tp>
1277  struct is_nothrow_move_assignable
1278  : public __is_nothrow_assignable_impl<__add_lval_ref_t<_Tp>,
1279  __add_rval_ref_t<_Tp>>
1280  {
1281  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1282  "template argument must be a complete class or an unbounded array");
1283  };
1284 
1285  /// @cond undocumented
1286  template<typename _Tp, typename... _Args>
1287  using __is_trivially_constructible_impl
1288  = __bool_constant<__is_trivially_constructible(_Tp, _Args...)>;
1289  /// @endcond
1290 
1291  /// is_trivially_constructible
1292  template<typename _Tp, typename... _Args>
1293  struct is_trivially_constructible
1294  : public __is_trivially_constructible_impl<_Tp, _Args...>
1295  {
1296  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1297  "template argument must be a complete class or an unbounded array");
1298  };
1299 
1300  /// is_trivially_default_constructible
1301  template<typename _Tp>
1302  struct is_trivially_default_constructible
1303  : public __is_trivially_constructible_impl<_Tp>
1304  {
1305  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1306  "template argument must be a complete class or an unbounded array");
1307  };
1308 
1309 #if __cpp_variable_templates && __cpp_concepts
1310  template<typename _Tp>
1311  constexpr bool __is_implicitly_default_constructible_v
1312  = requires (void(&__f)(_Tp)) { __f({}); };
1313 
1314  template<typename _Tp>
1315  struct __is_implicitly_default_constructible
1316  : __bool_constant<__is_implicitly_default_constructible_v<_Tp>>
1317  { };
1318 #else
1319  struct __do_is_implicitly_default_constructible_impl
1320  {
1321  template <typename _Tp>
1322  static void __helper(const _Tp&);
1323 
1324  template <typename _Tp>
1325  static true_type __test(const _Tp&,
1326  decltype(__helper<const _Tp&>({}))* = 0);
1327 
1328  static false_type __test(...);
1329  };
1330 
1331  template<typename _Tp>
1332  struct __is_implicitly_default_constructible_impl
1333  : public __do_is_implicitly_default_constructible_impl
1334  {
1335  using type = decltype(__test(declval<_Tp>()));
1336  };
1337 
1338  template<typename _Tp>
1339  struct __is_implicitly_default_constructible_safe
1340  : public __is_implicitly_default_constructible_impl<_Tp>::type
1341  { };
1342 
1343  template <typename _Tp>
1344  struct __is_implicitly_default_constructible
1345  : public __and_<__is_constructible_impl<_Tp>,
1346  __is_implicitly_default_constructible_safe<_Tp>>::type
1347  { };
1348 #endif
1349 
1350  /// is_trivially_copy_constructible
1351  template<typename _Tp>
1352  struct is_trivially_copy_constructible
1353  : public __is_trivially_constructible_impl<_Tp, __add_lval_ref_t<const _Tp>>
1354  {
1355  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1356  "template argument must be a complete class or an unbounded array");
1357  };
1358 
1359  /// is_trivially_move_constructible
1360  template<typename _Tp>
1361  struct is_trivially_move_constructible
1362  : public __is_trivially_constructible_impl<_Tp, __add_rval_ref_t<_Tp>>
1363  {
1364  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1365  "template argument must be a complete class or an unbounded array");
1366  };
1367 
1368  /// @cond undocumented
1369  template<typename _Tp, typename _Up>
1370  using __is_trivially_assignable_impl
1371  = __bool_constant<__is_trivially_assignable(_Tp, _Up)>;
1372  /// @endcond
1373 
1374  /// is_trivially_assignable
1375  template<typename _Tp, typename _Up>
1376  struct is_trivially_assignable
1377  : public __is_trivially_assignable_impl<_Tp, _Up>
1378  {
1379  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1380  "template argument must be a complete class or an unbounded array");
1381  };
1382 
1383  /// is_trivially_copy_assignable
1384  template<typename _Tp>
1385  struct is_trivially_copy_assignable
1386  : public __is_trivially_assignable_impl<__add_lval_ref_t<_Tp>,
1387  __add_lval_ref_t<const _Tp>>
1388  {
1389  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1390  "template argument must be a complete class or an unbounded array");
1391  };
1392 
1393  /// is_trivially_move_assignable
1394  template<typename _Tp>
1395  struct is_trivially_move_assignable
1396  : public __is_trivially_assignable_impl<__add_lval_ref_t<_Tp>,
1397  __add_rval_ref_t<_Tp>>
1398  {
1399  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1400  "template argument must be a complete class or an unbounded array");
1401  };
1402 
1403  /// is_trivially_destructible
1404  template<typename _Tp>
1405  struct is_trivially_destructible
1406  : public __and_<__is_destructible_safe<_Tp>,
1407  __bool_constant<__has_trivial_destructor(_Tp)>>::type
1408  {
1409  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1410  "template argument must be a complete class or an unbounded array");
1411  };
1412 
1413 
1414  /// has_virtual_destructor
1415  template<typename _Tp>
1416  struct has_virtual_destructor
1417  : public __bool_constant<__has_virtual_destructor(_Tp)>
1418  {
1419  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1420  "template argument must be a complete class or an unbounded array");
1421  };
1422 
1423 
1424  // type property queries.
1425 
1426  /// alignment_of
1427  template<typename _Tp>
1428  struct alignment_of
1429  : public integral_constant<std::size_t, alignof(_Tp)>
1430  {
1431  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1432  "template argument must be a complete class or an unbounded array");
1433  };
1434 
1435  /// rank
1436  template<typename>
1437  struct rank
1438  : public integral_constant<std::size_t, 0> { };
1439 
1440  template<typename _Tp, std::size_t _Size>
1441  struct rank<_Tp[_Size]>
1442  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1443 
1444  template<typename _Tp>
1445  struct rank<_Tp[]>
1446  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1447 
1448  /// extent
1449  template<typename, unsigned _Uint = 0>
1450  struct extent
1451  : public integral_constant<size_t, 0> { };
1452 
1453  template<typename _Tp, size_t _Size>
1454  struct extent<_Tp[_Size], 0>
1455  : public integral_constant<size_t, _Size> { };
1456 
1457  template<typename _Tp, unsigned _Uint, size_t _Size>
1458  struct extent<_Tp[_Size], _Uint>
1459  : public extent<_Tp, _Uint - 1>::type { };
1460 
1461  template<typename _Tp>
1462  struct extent<_Tp[], 0>
1463  : public integral_constant<size_t, 0> { };
1464 
1465  template<typename _Tp, unsigned _Uint>
1466  struct extent<_Tp[], _Uint>
1467  : public extent<_Tp, _Uint - 1>::type { };
1468 
1469 
1470  // Type relations.
1471 
1472  /// is_same
1473 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_same)
1474  template<typename _Tp, typename _Up>
1475  struct is_same
1476  : public __bool_constant<__is_same(_Tp, _Up)>
1477  { };
1478 #else
1479  template<typename _Tp, typename _Up>
1480  struct is_same
1481  : public false_type
1482  { };
1483 
1484  template<typename _Tp>
1485  struct is_same<_Tp, _Tp>
1486  : public true_type
1487  { };
1488 #endif
1489 
1490  /// is_base_of
1491  template<typename _Base, typename _Derived>
1492  struct is_base_of
1493  : public __bool_constant<__is_base_of(_Base, _Derived)>
1494  { };
1495 
1496 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_convertible)
1497  template<typename _From, typename _To>
1498  struct is_convertible
1499  : public __bool_constant<__is_convertible(_From, _To)>
1500  { };
1501 #else
1502  template<typename _From, typename _To,
1503  bool = __or_<is_void<_From>, is_function<_To>,
1504  is_array<_To>>::value>
1505  struct __is_convertible_helper
1506  {
1507  using type = typename is_void<_To>::type;
1508  };
1509 
1510 #pragma GCC diagnostic push
1511 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1512  template<typename _From, typename _To>
1513  class __is_convertible_helper<_From, _To, false>
1514  {
1515  template<typename _To1>
1516  static void __test_aux(_To1) noexcept;
1517 
1518  template<typename _From1, typename _To1,
1519  typename = decltype(__test_aux<_To1>(std::declval<_From1>()))>
1520  static true_type
1521  __test(int);
1522 
1523  template<typename, typename>
1524  static false_type
1525  __test(...);
1526 
1527  public:
1528  using type = decltype(__test<_From, _To>(0));
1529  };
1530 #pragma GCC diagnostic pop
1531 
1532  /// is_convertible
1533  template<typename _From, typename _To>
1534  struct is_convertible
1535  : public __is_convertible_helper<_From, _To>::type
1536  { };
1537 #endif
1538 
1539  // helper trait for unique_ptr<T[]>, shared_ptr<T[]>, and span<T, N>
1540  template<typename _ToElementType, typename _FromElementType>
1541  using __is_array_convertible
1542  = is_convertible<_FromElementType(*)[], _ToElementType(*)[]>;
1543 
1544 #ifdef __cpp_lib_is_nothrow_convertible // C++ >= 20
1545 
1546 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_nothrow_convertible)
1547  /// is_nothrow_convertible_v
1548  template<typename _From, typename _To>
1549  inline constexpr bool is_nothrow_convertible_v
1550  = __is_nothrow_convertible(_From, _To);
1551 
1552  /// is_nothrow_convertible
1553  template<typename _From, typename _To>
1554  struct is_nothrow_convertible
1555  : public bool_constant<is_nothrow_convertible_v<_From, _To>>
1556  { };
1557 #else
1558  template<typename _From, typename _To,
1559  bool = __or_<is_void<_From>, is_function<_To>,
1560  is_array<_To>>::value>
1561  struct __is_nt_convertible_helper
1562  : is_void<_To>
1563  { };
1564 
1565 #pragma GCC diagnostic push
1566 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1567  template<typename _From, typename _To>
1568  class __is_nt_convertible_helper<_From, _To, false>
1569  {
1570  template<typename _To1>
1571  static void __test_aux(_To1) noexcept;
1572 
1573  template<typename _From1, typename _To1>
1574  static
1575  __bool_constant<noexcept(__test_aux<_To1>(std::declval<_From1>()))>
1576  __test(int);
1577 
1578  template<typename, typename>
1579  static false_type
1580  __test(...);
1581 
1582  public:
1583  using type = decltype(__test<_From, _To>(0));
1584  };
1585 #pragma GCC diagnostic pop
1586 
1587  /// is_nothrow_convertible
1588  template<typename _From, typename _To>
1589  struct is_nothrow_convertible
1590  : public __is_nt_convertible_helper<_From, _To>::type
1591  { };
1592 
1593  /// is_nothrow_convertible_v
1594  template<typename _From, typename _To>
1595  inline constexpr bool is_nothrow_convertible_v
1596  = is_nothrow_convertible<_From, _To>::value;
1597 #endif
1598 #endif // __cpp_lib_is_nothrow_convertible
1599 
1600  // Const-volatile modifications.
1601 
1602  /// remove_const
1603  template<typename _Tp>
1604  struct remove_const
1605  { using type = _Tp; };
1606 
1607  template<typename _Tp>
1608  struct remove_const<_Tp const>
1609  { using type = _Tp; };
1610 
1611  /// remove_volatile
1612  template<typename _Tp>
1613  struct remove_volatile
1614  { using type = _Tp; };
1615 
1616  template<typename _Tp>
1617  struct remove_volatile<_Tp volatile>
1618  { using type = _Tp; };
1619 
1620  /// remove_cv
1621 #if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_cv)
1622  template<typename _Tp>
1623  struct remove_cv
1624  { using type = __remove_cv(_Tp); };
1625 #else
1626  template<typename _Tp>
1627  struct remove_cv
1628  { using type = _Tp; };
1629 
1630  template<typename _Tp>
1631  struct remove_cv<const _Tp>
1632  { using type = _Tp; };
1633 
1634  template<typename _Tp>
1635  struct remove_cv<volatile _Tp>
1636  { using type = _Tp; };
1637 
1638  template<typename _Tp>
1639  struct remove_cv<const volatile _Tp>
1640  { using type = _Tp; };
1641 #endif
1642 
1643  /// add_const
1644  template<typename _Tp>
1645  struct add_const
1646  { using type = _Tp const; };
1647 
1648  /// add_volatile
1649  template<typename _Tp>
1650  struct add_volatile
1651  { using type = _Tp volatile; };
1652 
1653  /// add_cv
1654  template<typename _Tp>
1655  struct add_cv
1656  { using type = _Tp const volatile; };
1657 
1658 #ifdef __cpp_lib_transformation_trait_aliases // C++ >= 14
1659  /// Alias template for remove_const
1660  template<typename _Tp>
1661  using remove_const_t = typename remove_const<_Tp>::type;
1662 
1663  /// Alias template for remove_volatile
1664  template<typename _Tp>
1665  using remove_volatile_t = typename remove_volatile<_Tp>::type;
1666 
1667  /// Alias template for remove_cv
1668  template<typename _Tp>
1669  using remove_cv_t = typename remove_cv<_Tp>::type;
1670 
1671  /// Alias template for add_const
1672  template<typename _Tp>
1673  using add_const_t = typename add_const<_Tp>::type;
1674 
1675  /// Alias template for add_volatile
1676  template<typename _Tp>
1677  using add_volatile_t = typename add_volatile<_Tp>::type;
1678 
1679  /// Alias template for add_cv
1680  template<typename _Tp>
1681  using add_cv_t = typename add_cv<_Tp>::type;
1682 #endif
1683 
1684  // Reference transformations.
1685 
1686  /// remove_reference
1687 #if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_reference)
1688  template<typename _Tp>
1689  struct remove_reference
1690  { using type = __remove_reference(_Tp); };
1691 #else
1692  template<typename _Tp>
1693  struct remove_reference
1694  { using type = _Tp; };
1695 
1696  template<typename _Tp>
1697  struct remove_reference<_Tp&>
1698  { using type = _Tp; };
1699 
1700  template<typename _Tp>
1701  struct remove_reference<_Tp&&>
1702  { using type = _Tp; };
1703 #endif
1704 
1705  /// add_lvalue_reference
1706  template<typename _Tp>
1707  struct add_lvalue_reference
1708  { using type = __add_lval_ref_t<_Tp>; };
1709 
1710  /// add_rvalue_reference
1711  template<typename _Tp>
1712  struct add_rvalue_reference
1713  { using type = __add_rval_ref_t<_Tp>; };
1714 
1715 #if __cplusplus > 201103L
1716  /// Alias template for remove_reference
1717  template<typename _Tp>
1718  using remove_reference_t = typename remove_reference<_Tp>::type;
1719 
1720  /// Alias template for add_lvalue_reference
1721  template<typename _Tp>
1722  using add_lvalue_reference_t = typename add_lvalue_reference<_Tp>::type;
1723 
1724  /// Alias template for add_rvalue_reference
1725  template<typename _Tp>
1726  using add_rvalue_reference_t = typename add_rvalue_reference<_Tp>::type;
1727 #endif
1728 
1729  // Sign modifications.
1730 
1731  /// @cond undocumented
1732 
1733  // Utility for constructing identically cv-qualified types.
1734  template<typename _Unqualified, bool _IsConst, bool _IsVol>
1735  struct __cv_selector;
1736 
1737  template<typename _Unqualified>
1738  struct __cv_selector<_Unqualified, false, false>
1739  { using __type = _Unqualified; };
1740 
1741  template<typename _Unqualified>
1742  struct __cv_selector<_Unqualified, false, true>
1743  { using __type = volatile _Unqualified; };
1744 
1745  template<typename _Unqualified>
1746  struct __cv_selector<_Unqualified, true, false>
1747  { using __type = const _Unqualified; };
1748 
1749  template<typename _Unqualified>
1750  struct __cv_selector<_Unqualified, true, true>
1751  { using __type = const volatile _Unqualified; };
1752 
1753  template<typename _Qualified, typename _Unqualified,
1754  bool _IsConst = is_const<_Qualified>::value,
1755  bool _IsVol = is_volatile<_Qualified>::value>
1756  class __match_cv_qualifiers
1757  {
1758  using __match = __cv_selector<_Unqualified, _IsConst, _IsVol>;
1759 
1760  public:
1761  using __type = typename __match::__type;
1762  };
1763 
1764  // Utility for finding the unsigned versions of signed integral types.
1765  template<typename _Tp>
1766  struct __make_unsigned
1767  { using __type = _Tp; };
1768 
1769  template<>
1770  struct __make_unsigned<char>
1771  { using __type = unsigned char; };
1772 
1773  template<>
1774  struct __make_unsigned<signed char>
1775  { using __type = unsigned char; };
1776 
1777  template<>
1778  struct __make_unsigned<short>
1779  { using __type = unsigned short; };
1780 
1781  template<>
1782  struct __make_unsigned<int>
1783  { using __type = unsigned int; };
1784 
1785  template<>
1786  struct __make_unsigned<long>
1787  { using __type = unsigned long; };
1788 
1789  template<>
1790  struct __make_unsigned<long long>
1791  { using __type = unsigned long long; };
1792 
1793 #if defined(__GLIBCXX_TYPE_INT_N_0)
1794  __extension__
1795  template<>
1796  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_0>
1797  { using __type = unsigned __GLIBCXX_TYPE_INT_N_0; };
1798 #endif
1799 #if defined(__GLIBCXX_TYPE_INT_N_1)
1800  __extension__
1801  template<>
1802  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_1>
1803  { using __type = unsigned __GLIBCXX_TYPE_INT_N_1; };
1804 #endif
1805 #if defined(__GLIBCXX_TYPE_INT_N_2)
1806  __extension__
1807  template<>
1808  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_2>
1809  { using __type = unsigned __GLIBCXX_TYPE_INT_N_2; };
1810 #endif
1811 #if defined(__GLIBCXX_TYPE_INT_N_3)
1812  __extension__
1813  template<>
1814  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_3>
1815  { using __type = unsigned __GLIBCXX_TYPE_INT_N_3; };
1816 #endif
1817 
1818  // Select between integral and enum: not possible to be both.
1819  template<typename _Tp,
1820  bool _IsInt = is_integral<_Tp>::value,
1821  bool _IsEnum = __is_enum(_Tp)>
1822  class __make_unsigned_selector;
1823 
1824  template<typename _Tp>
1825  class __make_unsigned_selector<_Tp, true, false>
1826  {
1827  using __unsigned_type
1828  = typename __make_unsigned<__remove_cv_t<_Tp>>::__type;
1829 
1830  public:
1831  using __type
1832  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1833  };
1834 
1835  class __make_unsigned_selector_base
1836  {
1837  protected:
1838  template<typename...> struct _List { };
1839 
1840  template<typename _Tp, typename... _Up>
1841  struct _List<_Tp, _Up...> : _List<_Up...>
1842  { static constexpr size_t __size = sizeof(_Tp); };
1843 
1844  template<size_t _Sz, typename _Tp, bool = (_Sz <= _Tp::__size)>
1845  struct __select;
1846 
1847  template<size_t _Sz, typename _Uint, typename... _UInts>
1848  struct __select<_Sz, _List<_Uint, _UInts...>, true>
1849  { using __type = _Uint; };
1850 
1851  template<size_t _Sz, typename _Uint, typename... _UInts>
1852  struct __select<_Sz, _List<_Uint, _UInts...>, false>
1853  : __select<_Sz, _List<_UInts...>>
1854  { };
1855  };
1856 
1857  // Choose unsigned integer type with the smallest rank and same size as _Tp
1858  template<typename _Tp>
1859  class __make_unsigned_selector<_Tp, false, true>
1860  : __make_unsigned_selector_base
1861  {
1862  // With -fshort-enums, an enum may be as small as a char.
1863  using _UInts = _List<unsigned char, unsigned short, unsigned int,
1864  unsigned long, unsigned long long>;
1865 
1866  using __unsigned_type = typename __select<sizeof(_Tp), _UInts>::__type;
1867 
1868  public:
1869  using __type
1870  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1871  };
1872 
1873  // wchar_t, char8_t, char16_t and char32_t are integral types but are
1874  // neither signed integer types nor unsigned integer types, so must be
1875  // transformed to the unsigned integer type with the smallest rank.
1876  // Use the partial specialization for enumeration types to do that.
1877  template<>
1878  struct __make_unsigned<wchar_t>
1879  {
1880  using __type
1881  = typename __make_unsigned_selector<wchar_t, false, true>::__type;
1882  };
1883 
1884 #ifdef _GLIBCXX_USE_CHAR8_T
1885  template<>
1886  struct __make_unsigned<char8_t>
1887  {
1888  using __type
1889  = typename __make_unsigned_selector<char8_t, false, true>::__type;
1890  };
1891 #endif
1892 
1893  template<>
1894  struct __make_unsigned<char16_t>
1895  {
1896  using __type
1897  = typename __make_unsigned_selector<char16_t, false, true>::__type;
1898  };
1899 
1900  template<>
1901  struct __make_unsigned<char32_t>
1902  {
1903  using __type
1904  = typename __make_unsigned_selector<char32_t, false, true>::__type;
1905  };
1906  /// @endcond
1907 
1908  // Given an integral/enum type, return the corresponding unsigned
1909  // integer type.
1910  // Primary template.
1911  /// make_unsigned
1912  template<typename _Tp>
1913  struct make_unsigned
1914  { using type = typename __make_unsigned_selector<_Tp>::__type; };
1915 
1916  // Integral, but don't define.
1917  template<> struct make_unsigned<bool>;
1918  template<> struct make_unsigned<bool const>;
1919  template<> struct make_unsigned<bool volatile>;
1920  template<> struct make_unsigned<bool const volatile>;
1921 
1922  /// @cond undocumented
1923 
1924  // Utility for finding the signed versions of unsigned integral types.
1925  template<typename _Tp>
1926  struct __make_signed
1927  { using __type = _Tp; };
1928 
1929  template<>
1930  struct __make_signed<char>
1931  { using __type = signed char; };
1932 
1933  template<>
1934  struct __make_signed<unsigned char>
1935  { using __type = signed char; };
1936 
1937  template<>
1938  struct __make_signed<unsigned short>
1939  { using __type = signed short; };
1940 
1941  template<>
1942  struct __make_signed<unsigned int>
1943  { using __type = signed int; };
1944 
1945  template<>
1946  struct __make_signed<unsigned long>
1947  { using __type = signed long; };
1948 
1949  template<>
1950  struct __make_signed<unsigned long long>
1951  { using __type = signed long long; };
1952 
1953 #if defined(__GLIBCXX_TYPE_INT_N_0)
1954  __extension__
1955  template<>
1956  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_0>
1957  { using __type = __GLIBCXX_TYPE_INT_N_0; };
1958 #endif
1959 #if defined(__GLIBCXX_TYPE_INT_N_1)
1960  __extension__
1961  template<>
1962  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_1>
1963  { using __type = __GLIBCXX_TYPE_INT_N_1; };
1964 #endif
1965 #if defined(__GLIBCXX_TYPE_INT_N_2)
1966  __extension__
1967  template<>
1968  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_2>
1969  { using __type = __GLIBCXX_TYPE_INT_N_2; };
1970 #endif
1971 #if defined(__GLIBCXX_TYPE_INT_N_3)
1972  __extension__
1973  template<>
1974  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_3>
1975  { using __type = __GLIBCXX_TYPE_INT_N_3; };
1976 #endif
1977 
1978  // Select between integral and enum: not possible to be both.
1979  template<typename _Tp,
1980  bool _IsInt = is_integral<_Tp>::value,
1981  bool _IsEnum = __is_enum(_Tp)>
1982  class __make_signed_selector;
1983 
1984  template<typename _Tp>
1985  class __make_signed_selector<_Tp, true, false>
1986  {
1987  using __signed_type
1988  = typename __make_signed<__remove_cv_t<_Tp>>::__type;
1989 
1990  public:
1991  using __type
1992  = typename __match_cv_qualifiers<_Tp, __signed_type>::__type;
1993  };
1994 
1995  // Choose signed integer type with the smallest rank and same size as _Tp
1996  template<typename _Tp>
1997  class __make_signed_selector<_Tp, false, true>
1998  {
1999  using __unsigned_type = typename __make_unsigned_selector<_Tp>::__type;
2000 
2001  public:
2002  using __type = typename __make_signed_selector<__unsigned_type>::__type;
2003  };
2004 
2005  // wchar_t, char16_t and char32_t are integral types but are neither
2006  // signed integer types nor unsigned integer types, so must be
2007  // transformed to the signed integer type with the smallest rank.
2008  // Use the partial specialization for enumeration types to do that.
2009  template<>
2010  struct __make_signed<wchar_t>
2011  {
2012  using __type
2013  = typename __make_signed_selector<wchar_t, false, true>::__type;
2014  };
2015 
2016 #if defined(_GLIBCXX_USE_CHAR8_T)
2017  template<>
2018  struct __make_signed<char8_t>
2019  {
2020  using __type
2021  = typename __make_signed_selector<char8_t, false, true>::__type;
2022  };
2023 #endif
2024 
2025  template<>
2026  struct __make_signed<char16_t>
2027  {
2028  using __type
2029  = typename __make_signed_selector<char16_t, false, true>::__type;
2030  };
2031 
2032  template<>
2033  struct __make_signed<char32_t>
2034  {
2035  using __type
2036  = typename __make_signed_selector<char32_t, false, true>::__type;
2037  };
2038  /// @endcond
2039 
2040  // Given an integral/enum type, return the corresponding signed
2041  // integer type.
2042  // Primary template.
2043  /// make_signed
2044  template<typename _Tp>
2045  struct make_signed
2046  { using type = typename __make_signed_selector<_Tp>::__type; };
2047 
2048  // Integral, but don't define.
2049  template<> struct make_signed<bool>;
2050  template<> struct make_signed<bool const>;
2051  template<> struct make_signed<bool volatile>;
2052  template<> struct make_signed<bool const volatile>;
2053 
2054 #if __cplusplus > 201103L
2055  /// Alias template for make_signed
2056  template<typename _Tp>
2057  using make_signed_t = typename make_signed<_Tp>::type;
2058 
2059  /// Alias template for make_unsigned
2060  template<typename _Tp>
2061  using make_unsigned_t = typename make_unsigned<_Tp>::type;
2062 #endif
2063 
2064  // Array modifications.
2065 
2066  /// remove_extent
2067  template<typename _Tp>
2068  struct remove_extent
2069  { using type = _Tp; };
2070 
2071  template<typename _Tp, std::size_t _Size>
2072  struct remove_extent<_Tp[_Size]>
2073  { using type = _Tp; };
2074 
2075  template<typename _Tp>
2076  struct remove_extent<_Tp[]>
2077  { using type = _Tp; };
2078 
2079  /// remove_all_extents
2080  template<typename _Tp>
2081  struct remove_all_extents
2082  { using type = _Tp; };
2083 
2084  template<typename _Tp, std::size_t _Size>
2085  struct remove_all_extents<_Tp[_Size]>
2086  { using type = typename remove_all_extents<_Tp>::type; };
2087 
2088  template<typename _Tp>
2089  struct remove_all_extents<_Tp[]>
2090  { using type = typename remove_all_extents<_Tp>::type; };
2091 
2092 #if __cplusplus > 201103L
2093  /// Alias template for remove_extent
2094  template<typename _Tp>
2095  using remove_extent_t = typename remove_extent<_Tp>::type;
2096 
2097  /// Alias template for remove_all_extents
2098  template<typename _Tp>
2099  using remove_all_extents_t = typename remove_all_extents<_Tp>::type;
2100 #endif
2101 
2102  // Pointer modifications.
2103 
2104  /// remove_pointer
2105 #if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_pointer)
2106  template<typename _Tp>
2107  struct remove_pointer
2108  { using type = __remove_pointer(_Tp); };
2109 #else
2110  template<typename _Tp, typename>
2111  struct __remove_pointer_helper
2112  { using type = _Tp; };
2113 
2114  template<typename _Tp, typename _Up>
2115  struct __remove_pointer_helper<_Tp, _Up*>
2116  { using type = _Up; };
2117 
2118  template<typename _Tp>
2119  struct remove_pointer
2120  : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
2121  { };
2122 #endif
2123 
2124  template<typename _Tp, typename = void>
2125  struct __add_pointer_helper
2126  { using type = _Tp; };
2127 
2128  template<typename _Tp>
2129  struct __add_pointer_helper<_Tp, __void_t<_Tp*>>
2130  { using type = _Tp*; };
2131 
2132  /// add_pointer
2133  template<typename _Tp>
2134  struct add_pointer
2135  : public __add_pointer_helper<_Tp>
2136  { };
2137 
2138  template<typename _Tp>
2139  struct add_pointer<_Tp&>
2140  { using type = _Tp*; };
2141 
2142  template<typename _Tp>
2143  struct add_pointer<_Tp&&>
2144  { using type = _Tp*; };
2145 
2146 #if __cplusplus > 201103L
2147  /// Alias template for remove_pointer
2148  template<typename _Tp>
2149  using remove_pointer_t = typename remove_pointer<_Tp>::type;
2150 
2151  /// Alias template for add_pointer
2152  template<typename _Tp>
2153  using add_pointer_t = typename add_pointer<_Tp>::type;
2154 #endif
2155 
2156  template<std::size_t _Len>
2157  struct __aligned_storage_msa
2158  {
2159  union __type
2160  {
2161  unsigned char __data[_Len];
2162  struct __attribute__((__aligned__)) { } __align;
2163  };
2164  };
2165 
2166  /**
2167  * @brief Alignment type.
2168  *
2169  * The value of _Align is a default-alignment which shall be the
2170  * most stringent alignment requirement for any C++ object type
2171  * whose size is no greater than _Len (3.9). The member typedef
2172  * type shall be a POD type suitable for use as uninitialized
2173  * storage for any object whose size is at most _Len and whose
2174  * alignment is a divisor of _Align.
2175  *
2176  * @deprecated Deprecated in C++23. Uses can be replaced by an
2177  * array std::byte[_Len] declared with alignas(_Align).
2178  */
2179  template<std::size_t _Len, std::size_t _Align =
2180  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2181  struct
2182  _GLIBCXX23_DEPRECATED
2183  aligned_storage
2184  {
2185  union type
2186  {
2187  unsigned char __data[_Len];
2188  struct __attribute__((__aligned__((_Align)))) { } __align;
2189  };
2190  };
2191 
2192  template <typename... _Types>
2193  struct __strictest_alignment
2194  {
2195  static const size_t _S_alignment = 0;
2196  static const size_t _S_size = 0;
2197  };
2198 
2199  template <typename _Tp, typename... _Types>
2200  struct __strictest_alignment<_Tp, _Types...>
2201  {
2202  static const size_t _S_alignment =
2203  alignof(_Tp) > __strictest_alignment<_Types...>::_S_alignment
2204  ? alignof(_Tp) : __strictest_alignment<_Types...>::_S_alignment;
2205  static const size_t _S_size =
2206  sizeof(_Tp) > __strictest_alignment<_Types...>::_S_size
2207  ? sizeof(_Tp) : __strictest_alignment<_Types...>::_S_size;
2208  };
2209 
2210 #pragma GCC diagnostic push
2211 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
2212 
2213  /**
2214  * @brief Provide aligned storage for types.
2215  *
2216  * [meta.trans.other]
2217  *
2218  * Provides aligned storage for any of the provided types of at
2219  * least size _Len.
2220  *
2221  * @see aligned_storage
2222  *
2223  * @deprecated Deprecated in C++23.
2224  */
2225  template <size_t _Len, typename... _Types>
2226  struct
2227  _GLIBCXX23_DEPRECATED
2228  aligned_union
2229  {
2230  private:
2231  static_assert(sizeof...(_Types) != 0, "At least one type is required");
2232 
2233  using __strictest = __strictest_alignment<_Types...>;
2234  static const size_t _S_len = _Len > __strictest::_S_size
2235  ? _Len : __strictest::_S_size;
2236  public:
2237  /// The value of the strictest alignment of _Types.
2238  static const size_t alignment_value = __strictest::_S_alignment;
2239  /// The storage.
2240  using type = typename aligned_storage<_S_len, alignment_value>::type;
2241  };
2242 
2243  template <size_t _Len, typename... _Types>
2244  const size_t aligned_union<_Len, _Types...>::alignment_value;
2245 #pragma GCC diagnostic pop
2246 
2247  /// @cond undocumented
2248 
2249  // Decay trait for arrays and functions, used for perfect forwarding
2250  // in make_pair, make_tuple, etc.
2251  template<typename _Up>
2252  struct __decay_selector
2253  : __conditional_t<is_const<const _Up>::value, // false for functions
2254  remove_cv<_Up>, // N.B. DR 705.
2255  add_pointer<_Up>> // function decays to pointer
2256  { };
2257 
2258  template<typename _Up, size_t _Nm>
2259  struct __decay_selector<_Up[_Nm]>
2260  { using type = _Up*; };
2261 
2262  template<typename _Up>
2263  struct __decay_selector<_Up[]>
2264  { using type = _Up*; };
2265 
2266  /// @endcond
2267 
2268  /// decay
2269  template<typename _Tp>
2270  struct decay
2271  { using type = typename __decay_selector<_Tp>::type; };
2272 
2273  template<typename _Tp>
2274  struct decay<_Tp&>
2275  { using type = typename __decay_selector<_Tp>::type; };
2276 
2277  template<typename _Tp>
2278  struct decay<_Tp&&>
2279  { using type = typename __decay_selector<_Tp>::type; };
2280 
2281  /// @cond undocumented
2282 
2283  // Helper which adds a reference to a type when given a reference_wrapper
2284  template<typename _Tp>
2285  struct __strip_reference_wrapper
2286  {
2287  using __type = _Tp;
2288  };
2289 
2290  template<typename _Tp>
2291  struct __strip_reference_wrapper<reference_wrapper<_Tp> >
2292  {
2293  using __type = _Tp&;
2294  };
2295 
2296  // __decay_t (std::decay_t for C++11).
2297  template<typename _Tp>
2298  using __decay_t = typename decay<_Tp>::type;
2299 
2300  template<typename _Tp>
2301  using __decay_and_strip = __strip_reference_wrapper<__decay_t<_Tp>>;
2302  /// @endcond
2303 
2304  /// @cond undocumented
2305 
2306  // Helper for SFINAE constraints
2307  template<typename... _Cond>
2308  using _Require = __enable_if_t<__and_<_Cond...>::value>;
2309 
2310  // __remove_cvref_t (std::remove_cvref_t for C++11).
2311  template<typename _Tp>
2312  using __remove_cvref_t
2313  = typename remove_cv<typename remove_reference<_Tp>::type>::type;
2314  /// @endcond
2315 
2316  // Primary template.
2317  /// Define a member typedef @c type to one of two argument types.
2318  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2319  struct conditional
2320  { using type = _Iftrue; };
2321 
2322  // Partial specialization for false.
2323  template<typename _Iftrue, typename _Iffalse>
2324  struct conditional<false, _Iftrue, _Iffalse>
2325  { using type = _Iffalse; };
2326 
2327  /// common_type
2328  template<typename... _Tp>
2329  struct common_type;
2330 
2331  // Sfinae-friendly common_type implementation:
2332 
2333  /// @cond undocumented
2334 
2335  // For several sfinae-friendly trait implementations we transport both the
2336  // result information (as the member type) and the failure information (no
2337  // member type). This is very similar to std::enable_if, but we cannot use
2338  // that, because we need to derive from them as an implementation detail.
2339 
2340  template<typename _Tp>
2341  struct __success_type
2342  { using type = _Tp; };
2343 
2344  struct __failure_type
2345  { };
2346 
2347  struct __do_common_type_impl
2348  {
2349  template<typename _Tp, typename _Up>
2350  using __cond_t
2351  = decltype(true ? std::declval<_Tp>() : std::declval<_Up>());
2352 
2353  // if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2354  // denotes a valid type, let C denote that type.
2355  template<typename _Tp, typename _Up>
2356  static __success_type<__decay_t<__cond_t<_Tp, _Up>>>
2357  _S_test(int);
2358 
2359 #if __cplusplus > 201703L
2360  // Otherwise, if COND-RES(CREF(D1), CREF(D2)) denotes a type,
2361  // let C denote the type decay_t<COND-RES(CREF(D1), CREF(D2))>.
2362  template<typename _Tp, typename _Up>
2363  static __success_type<__remove_cvref_t<__cond_t<const _Tp&, const _Up&>>>
2364  _S_test_2(int);
2365 #endif
2366 
2367  template<typename, typename>
2368  static __failure_type
2369  _S_test_2(...);
2370 
2371  template<typename _Tp, typename _Up>
2372  static decltype(_S_test_2<_Tp, _Up>(0))
2373  _S_test(...);
2374  };
2375 
2376  // If sizeof...(T) is zero, there shall be no member type.
2377  template<>
2378  struct common_type<>
2379  { };
2380 
2381  // If sizeof...(T) is one, the same type, if any, as common_type_t<T0, T0>.
2382  template<typename _Tp0>
2383  struct common_type<_Tp0>
2384  : public common_type<_Tp0, _Tp0>
2385  { };
2386 
2387  // If sizeof...(T) is two, ...
2388  template<typename _Tp1, typename _Tp2,
2389  typename _Dp1 = __decay_t<_Tp1>, typename _Dp2 = __decay_t<_Tp2>>
2390  struct __common_type_impl
2391  {
2392  // If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false,
2393  // let C denote the same type, if any, as common_type_t<D1, D2>.
2394  using type = common_type<_Dp1, _Dp2>;
2395  };
2396 
2397  template<typename _Tp1, typename _Tp2>
2398  struct __common_type_impl<_Tp1, _Tp2, _Tp1, _Tp2>
2399  : private __do_common_type_impl
2400  {
2401  // Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2402  // denotes a valid type, let C denote that type.
2403  using type = decltype(_S_test<_Tp1, _Tp2>(0));
2404  };
2405 
2406  // If sizeof...(T) is two, ...
2407  template<typename _Tp1, typename _Tp2>
2408  struct common_type<_Tp1, _Tp2>
2409  : public __common_type_impl<_Tp1, _Tp2>::type
2410  { };
2411 
2412  template<typename...>
2413  struct __common_type_pack
2414  { };
2415 
2416  template<typename, typename, typename = void>
2417  struct __common_type_fold;
2418 
2419  // If sizeof...(T) is greater than two, ...
2420  template<typename _Tp1, typename _Tp2, typename... _Rp>
2421  struct common_type<_Tp1, _Tp2, _Rp...>
2422  : public __common_type_fold<common_type<_Tp1, _Tp2>,
2423  __common_type_pack<_Rp...>>
2424  { };
2425 
2426  // Let C denote the same type, if any, as common_type_t<T1, T2>.
2427  // If there is such a type C, type shall denote the same type, if any,
2428  // as common_type_t<C, R...>.
2429  template<typename _CTp, typename... _Rp>
2430  struct __common_type_fold<_CTp, __common_type_pack<_Rp...>,
2431  __void_t<typename _CTp::type>>
2432  : public common_type<typename _CTp::type, _Rp...>
2433  { };
2434 
2435  // Otherwise, there shall be no member type.
2436  template<typename _CTp, typename _Rp>
2437  struct __common_type_fold<_CTp, _Rp, void>
2438  { };
2439 
2440  template<typename _Tp, bool = __is_enum(_Tp)>
2441  struct __underlying_type_impl
2442  {
2443  using type = __underlying_type(_Tp);
2444  };
2445 
2446  template<typename _Tp>
2447  struct __underlying_type_impl<_Tp, false>
2448  { };
2449  /// @endcond
2450 
2451  /// The underlying type of an enum.
2452  template<typename _Tp>
2453  struct underlying_type
2454  : public __underlying_type_impl<_Tp>
2455  { };
2456 
2457  /// @cond undocumented
2458  template<typename _Tp>
2459  struct __declval_protector
2460  {
2461  static const bool __stop = false;
2462  };
2463  /// @endcond
2464 
2465  /** Utility to simplify expressions used in unevaluated operands
2466  * @since C++11
2467  * @ingroup utilities
2468  */
2469  template<typename _Tp>
2470  auto declval() noexcept -> decltype(__declval<_Tp>(0))
2471  {
2472  static_assert(__declval_protector<_Tp>::__stop,
2473  "declval() must not be used!");
2474  return __declval<_Tp>(0);
2475  }
2476 
2477  /// result_of
2478  template<typename _Signature>
2479  struct result_of;
2480 
2481  // Sfinae-friendly result_of implementation:
2482 
2483  /// @cond undocumented
2484  struct __invoke_memfun_ref { };
2485  struct __invoke_memfun_deref { };
2486  struct __invoke_memobj_ref { };
2487  struct __invoke_memobj_deref { };
2488  struct __invoke_other { };
2489 
2490  // Associate a tag type with a specialization of __success_type.
2491  template<typename _Tp, typename _Tag>
2492  struct __result_of_success : __success_type<_Tp>
2493  { using __invoke_type = _Tag; };
2494 
2495  // [func.require] paragraph 1 bullet 1:
2496  struct __result_of_memfun_ref_impl
2497  {
2498  template<typename _Fp, typename _Tp1, typename... _Args>
2499  static __result_of_success<decltype(
2500  (std::declval<_Tp1>().*std::declval<_Fp>())(std::declval<_Args>()...)
2501  ), __invoke_memfun_ref> _S_test(int);
2502 
2503  template<typename...>
2504  static __failure_type _S_test(...);
2505  };
2506 
2507  template<typename _MemPtr, typename _Arg, typename... _Args>
2508  struct __result_of_memfun_ref
2509  : private __result_of_memfun_ref_impl
2510  {
2511  using type = decltype(_S_test<_MemPtr, _Arg, _Args...>(0));
2512  };
2513 
2514  // [func.require] paragraph 1 bullet 2:
2515  struct __result_of_memfun_deref_impl
2516  {
2517  template<typename _Fp, typename _Tp1, typename... _Args>
2518  static __result_of_success<decltype(
2519  ((*std::declval<_Tp1>()).*std::declval<_Fp>())(std::declval<_Args>()...)
2520  ), __invoke_memfun_deref> _S_test(int);
2521 
2522  template<typename...>
2523  static __failure_type _S_test(...);
2524  };
2525 
2526  template<typename _MemPtr, typename _Arg, typename... _Args>
2527  struct __result_of_memfun_deref
2528  : private __result_of_memfun_deref_impl
2529  {
2530  using type = decltype(_S_test<_MemPtr, _Arg, _Args...>(0));
2531  };
2532 
2533  // [func.require] paragraph 1 bullet 3:
2534  struct __result_of_memobj_ref_impl
2535  {
2536  template<typename _Fp, typename _Tp1>
2537  static __result_of_success<decltype(
2538  std::declval<_Tp1>().*std::declval<_Fp>()
2539  ), __invoke_memobj_ref> _S_test(int);
2540 
2541  template<typename, typename>
2542  static __failure_type _S_test(...);
2543  };
2544 
2545  template<typename _MemPtr, typename _Arg>
2546  struct __result_of_memobj_ref
2547  : private __result_of_memobj_ref_impl
2548  {
2549  using type = decltype(_S_test<_MemPtr, _Arg>(0));
2550  };
2551 
2552  // [func.require] paragraph 1 bullet 4:
2553  struct __result_of_memobj_deref_impl
2554  {
2555  template<typename _Fp, typename _Tp1>
2556  static __result_of_success<decltype(
2557  (*std::declval<_Tp1>()).*std::declval<_Fp>()
2558  ), __invoke_memobj_deref> _S_test(int);
2559 
2560  template<typename, typename>
2561  static __failure_type _S_test(...);
2562  };
2563 
2564  template<typename _MemPtr, typename _Arg>
2565  struct __result_of_memobj_deref
2566  : private __result_of_memobj_deref_impl
2567  {
2568  using type = decltype(_S_test<_MemPtr, _Arg>(0));
2569  };
2570 
2571  template<typename _MemPtr, typename _Arg>
2572  struct __result_of_memobj;
2573 
2574  template<typename _Res, typename _Class, typename _Arg>
2575  struct __result_of_memobj<_Res _Class::*, _Arg>
2576  {
2577  using _Argval = __remove_cvref_t<_Arg>;
2578  using _MemPtr = _Res _Class::*;
2579  using type = typename __conditional_t<__or_<is_same<_Argval, _Class>,
2580  is_base_of<_Class, _Argval>>::value,
2581  __result_of_memobj_ref<_MemPtr, _Arg>,
2582  __result_of_memobj_deref<_MemPtr, _Arg>
2583  >::type;
2584  };
2585 
2586  template<typename _MemPtr, typename _Arg, typename... _Args>
2587  struct __result_of_memfun;
2588 
2589  template<typename _Res, typename _Class, typename _Arg, typename... _Args>
2590  struct __result_of_memfun<_Res _Class::*, _Arg, _Args...>
2591  {
2592  using _Argval = typename remove_reference<_Arg>::type;
2593  using _MemPtr = _Res _Class::*;
2594  using type = typename __conditional_t<is_base_of<_Class, _Argval>::value,
2595  __result_of_memfun_ref<_MemPtr, _Arg, _Args...>,
2596  __result_of_memfun_deref<_MemPtr, _Arg, _Args...>
2597  >::type;
2598  };
2599 
2600  // _GLIBCXX_RESOLVE_LIB_DEFECTS
2601  // 2219. INVOKE-ing a pointer to member with a reference_wrapper
2602  // as the object expression
2603 
2604  // Used by result_of, invoke etc. to unwrap a reference_wrapper.
2605  template<typename _Tp, typename _Up = __remove_cvref_t<_Tp>>
2606  struct __inv_unwrap
2607  {
2608  using type = _Tp;
2609  };
2610 
2611  template<typename _Tp, typename _Up>
2612  struct __inv_unwrap<_Tp, reference_wrapper<_Up>>
2613  {
2614  using type = _Up&;
2615  };
2616 
2617  template<bool, bool, typename _Functor, typename... _ArgTypes>
2618  struct __result_of_impl
2619  {
2620  using type = __failure_type;
2621  };
2622 
2623  template<typename _MemPtr, typename _Arg>
2624  struct __result_of_impl<true, false, _MemPtr, _Arg>
2625  : public __result_of_memobj<__decay_t<_MemPtr>,
2626  typename __inv_unwrap<_Arg>::type>
2627  { };
2628 
2629  template<typename _MemPtr, typename _Arg, typename... _Args>
2630  struct __result_of_impl<false, true, _MemPtr, _Arg, _Args...>
2631  : public __result_of_memfun<__decay_t<_MemPtr>,
2632  typename __inv_unwrap<_Arg>::type, _Args...>
2633  { };
2634 
2635  // [func.require] paragraph 1 bullet 5:
2636  struct __result_of_other_impl
2637  {
2638  template<typename _Fn, typename... _Args>
2639  static __result_of_success<decltype(
2640  std::declval<_Fn>()(std::declval<_Args>()...)
2641  ), __invoke_other> _S_test(int);
2642 
2643  template<typename...>
2644  static __failure_type _S_test(...);
2645  };
2646 
2647  template<typename _Functor, typename... _ArgTypes>
2648  struct __result_of_impl<false, false, _Functor, _ArgTypes...>
2649  : private __result_of_other_impl
2650  {
2651  using type = decltype(_S_test<_Functor, _ArgTypes...>(0));
2652  };
2653 
2654  // __invoke_result (std::invoke_result for C++11)
2655  template<typename _Functor, typename... _ArgTypes>
2656  struct __invoke_result
2657  : public __result_of_impl<
2658  is_member_object_pointer<
2659  typename remove_reference<_Functor>::type
2660  >::value,
2661  is_member_function_pointer<
2662  typename remove_reference<_Functor>::type
2663  >::value,
2664  _Functor, _ArgTypes...
2665  >::type
2666  { };
2667 
2668  // __invoke_result_t (std::invoke_result_t for C++11)
2669  template<typename _Fn, typename... _Args>
2670  using __invoke_result_t = typename __invoke_result<_Fn, _Args...>::type;
2671  /// @endcond
2672 
2673  template<typename _Functor, typename... _ArgTypes>
2674  struct result_of<_Functor(_ArgTypes...)>
2675  : public __invoke_result<_Functor, _ArgTypes...>
2676  { } _GLIBCXX17_DEPRECATED_SUGGEST("std::invoke_result");
2677 
2678 #if __cplusplus >= 201402L
2679 #pragma GCC diagnostic push
2680 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
2681  /// Alias template for aligned_storage
2682  template<size_t _Len, size_t _Align =
2683  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2684  using aligned_storage_t _GLIBCXX23_DEPRECATED = typename aligned_storage<_Len, _Align>::type;
2685 
2686  template <size_t _Len, typename... _Types>
2687  using aligned_union_t _GLIBCXX23_DEPRECATED = typename aligned_union<_Len, _Types...>::type;
2688 #pragma GCC diagnostic pop
2689 
2690  /// Alias template for decay
2691  template<typename _Tp>
2692  using decay_t = typename decay<_Tp>::type;
2693 
2694  /// Alias template for enable_if
2695  template<bool _Cond, typename _Tp = void>
2696  using enable_if_t = typename enable_if<_Cond, _Tp>::type;
2697 
2698  /// Alias template for conditional
2699  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2700  using conditional_t = typename conditional<_Cond, _Iftrue, _Iffalse>::type;
2701 
2702  /// Alias template for common_type
2703  template<typename... _Tp>
2704  using common_type_t = typename common_type<_Tp...>::type;
2705 
2706  /// Alias template for underlying_type
2707  template<typename _Tp>
2708  using underlying_type_t = typename underlying_type<_Tp>::type;
2709 
2710  /// Alias template for result_of
2711  template<typename _Tp>
2712  using result_of_t = typename result_of<_Tp>::type;
2713 #endif // C++14
2714 
2715 #ifdef __cpp_lib_void_t // C++ >= 17 || GNU++ >= 11
2716  /// A metafunction that always yields void, used for detecting valid types.
2717  template<typename...> using void_t = void;
2718 #endif
2719 
2720  /// @cond undocumented
2721 
2722  // Detection idiom.
2723  // Detect whether _Op<_Args...> is a valid type, use default _Def if not.
2724 
2725 #if __cpp_concepts
2726  // Implementation of the detection idiom (negative case).
2727  template<typename _Def, template<typename...> class _Op, typename... _Args>
2728  struct __detected_or
2729  {
2730  using type = _Def;
2731  using __is_detected = false_type;
2732  };
2733 
2734  // Implementation of the detection idiom (positive case).
2735  template<typename _Def, template<typename...> class _Op, typename... _Args>
2736  requires requires { typename _Op<_Args...>; }
2737  struct __detected_or<_Def, _Op, _Args...>
2738  {
2739  using type = _Op<_Args...>;
2740  using __is_detected = true_type;
2741  };
2742 #else
2743  /// Implementation of the detection idiom (negative case).
2744  template<typename _Default, typename _AlwaysVoid,
2745  template<typename...> class _Op, typename... _Args>
2746  struct __detector
2747  {
2748  using type = _Default;
2749  using __is_detected = false_type;
2750  };
2751 
2752  /// Implementation of the detection idiom (positive case).
2753  template<typename _Default, template<typename...> class _Op,
2754  typename... _Args>
2755  struct __detector<_Default, __void_t<_Op<_Args...>>, _Op, _Args...>
2756  {
2757  using type = _Op<_Args...>;
2758  using __is_detected = true_type;
2759  };
2760 
2761  template<typename _Default, template<typename...> class _Op,
2762  typename... _Args>
2763  using __detected_or = __detector<_Default, void, _Op, _Args...>;
2764 #endif // __cpp_concepts
2765 
2766  // _Op<_Args...> if that is a valid type, otherwise _Default.
2767  template<typename _Default, template<typename...> class _Op,
2768  typename... _Args>
2769  using __detected_or_t
2770  = typename __detected_or<_Default, _Op, _Args...>::type;
2771 
2772  /**
2773  * Use SFINAE to determine if the type _Tp has a publicly-accessible
2774  * member type _NTYPE.
2775  */
2776 #define _GLIBCXX_HAS_NESTED_TYPE(_NTYPE) \
2777  template<typename _Tp, typename = __void_t<>> \
2778  struct __has_##_NTYPE \
2779  : false_type \
2780  { }; \
2781  template<typename _Tp> \
2782  struct __has_##_NTYPE<_Tp, __void_t<typename _Tp::_NTYPE>> \
2783  : true_type \
2784  { };
2785 
2786  template <typename _Tp>
2787  struct __is_swappable;
2788 
2789  template <typename _Tp>
2790  struct __is_nothrow_swappable;
2791 
2792  template<typename>
2793  struct __is_tuple_like_impl : false_type
2794  { };
2795 
2796  // Internal type trait that allows us to sfinae-protect tuple_cat.
2797  template<typename _Tp>
2798  struct __is_tuple_like
2799  : public __is_tuple_like_impl<__remove_cvref_t<_Tp>>::type
2800  { };
2801  /// @endcond
2802 
2803  template<typename _Tp>
2804  _GLIBCXX20_CONSTEXPR
2805  inline
2806  _Require<__not_<__is_tuple_like<_Tp>>,
2807  is_move_constructible<_Tp>,
2808  is_move_assignable<_Tp>>
2809  swap(_Tp&, _Tp&)
2810  noexcept(__and_<is_nothrow_move_constructible<_Tp>,
2811  is_nothrow_move_assignable<_Tp>>::value);
2812 
2813  template<typename _Tp, size_t _Nm>
2814  _GLIBCXX20_CONSTEXPR
2815  inline
2816  __enable_if_t<__is_swappable<_Tp>::value>
2817  swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
2818  noexcept(__is_nothrow_swappable<_Tp>::value);
2819 
2820  /// @cond undocumented
2821  namespace __swappable_details {
2822  using std::swap;
2823 
2824  struct __do_is_swappable_impl
2825  {
2826  template<typename _Tp, typename
2827  = decltype(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))>
2828  static true_type __test(int);
2829 
2830  template<typename>
2831  static false_type __test(...);
2832  };
2833 
2834  struct __do_is_nothrow_swappable_impl
2835  {
2836  template<typename _Tp>
2837  static __bool_constant<
2838  noexcept(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))
2839  > __test(int);
2840 
2841  template<typename>
2842  static false_type __test(...);
2843  };
2844 
2845  } // namespace __swappable_details
2846 
2847  template<typename _Tp>
2848  struct __is_swappable_impl
2849  : public __swappable_details::__do_is_swappable_impl
2850  {
2851  using type = decltype(__test<_Tp>(0));
2852  };
2853 
2854  template<typename _Tp>
2855  struct __is_nothrow_swappable_impl
2856  : public __swappable_details::__do_is_nothrow_swappable_impl
2857  {
2858  using type = decltype(__test<_Tp>(0));
2859  };
2860 
2861  template<typename _Tp>
2862  struct __is_swappable
2863  : public __is_swappable_impl<_Tp>::type
2864  { };
2865 
2866  template<typename _Tp>
2867  struct __is_nothrow_swappable
2868  : public __is_nothrow_swappable_impl<_Tp>::type
2869  { };
2870  /// @endcond
2871 
2872 #ifdef __cpp_lib_is_swappable // C++ >= 17 || GNU++ >= 11
2873  /// Metafunctions used for detecting swappable types: p0185r1
2874 
2875  /// is_swappable
2876  template<typename _Tp>
2877  struct is_swappable
2878  : public __is_swappable_impl<_Tp>::type
2879  {
2880  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2881  "template argument must be a complete class or an unbounded array");
2882  };
2883 
2884  /// is_nothrow_swappable
2885  template<typename _Tp>
2886  struct is_nothrow_swappable
2887  : public __is_nothrow_swappable_impl<_Tp>::type
2888  {
2889  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2890  "template argument must be a complete class or an unbounded array");
2891  };
2892 
2893 #if __cplusplus >= 201402L
2894  /// is_swappable_v
2895  template<typename _Tp>
2896  _GLIBCXX17_INLINE constexpr bool is_swappable_v =
2897  is_swappable<_Tp>::value;
2898 
2899  /// is_nothrow_swappable_v
2900  template<typename _Tp>
2901  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_v =
2902  is_nothrow_swappable<_Tp>::value;
2903 #endif // __cplusplus >= 201402L
2904 
2905  /// @cond undocumented
2906  namespace __swappable_with_details {
2907  using std::swap;
2908 
2909  struct __do_is_swappable_with_impl
2910  {
2911  template<typename _Tp, typename _Up, typename
2912  = decltype(swap(std::declval<_Tp>(), std::declval<_Up>())),
2913  typename
2914  = decltype(swap(std::declval<_Up>(), std::declval<_Tp>()))>
2915  static true_type __test(int);
2916 
2917  template<typename, typename>
2918  static false_type __test(...);
2919  };
2920 
2921  struct __do_is_nothrow_swappable_with_impl
2922  {
2923  template<typename _Tp, typename _Up>
2924  static __bool_constant<
2925  noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()))
2926  &&
2927  noexcept(swap(std::declval<_Up>(), std::declval<_Tp>()))
2928  > __test(int);
2929 
2930  template<typename, typename>
2931  static false_type __test(...);
2932  };
2933 
2934  } // namespace __swappable_with_details
2935 
2936  template<typename _Tp, typename _Up>
2937  struct __is_swappable_with_impl
2938  : public __swappable_with_details::__do_is_swappable_with_impl
2939  {
2940  using type = decltype(__test<_Tp, _Up>(0));
2941  };
2942 
2943  // Optimization for the homogenous lvalue case, not required:
2944  template<typename _Tp>
2945  struct __is_swappable_with_impl<_Tp&, _Tp&>
2946  : public __swappable_details::__do_is_swappable_impl
2947  {
2948  using type = decltype(__test<_Tp&>(0));
2949  };
2950 
2951  template<typename _Tp, typename _Up>
2952  struct __is_nothrow_swappable_with_impl
2953  : public __swappable_with_details::__do_is_nothrow_swappable_with_impl
2954  {
2955  using type = decltype(__test<_Tp, _Up>(0));
2956  };
2957 
2958  // Optimization for the homogenous lvalue case, not required:
2959  template<typename _Tp>
2960  struct __is_nothrow_swappable_with_impl<_Tp&, _Tp&>
2961  : public __swappable_details::__do_is_nothrow_swappable_impl
2962  {
2963  using type = decltype(__test<_Tp&>(0));
2964  };
2965  /// @endcond
2966 
2967  /// is_swappable_with
2968  template<typename _Tp, typename _Up>
2969  struct is_swappable_with
2970  : public __is_swappable_with_impl<_Tp, _Up>::type
2971  {
2972  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2973  "first template argument must be a complete class or an unbounded array");
2974  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2975  "second template argument must be a complete class or an unbounded array");
2976  };
2977 
2978  /// is_nothrow_swappable_with
2979  template<typename _Tp, typename _Up>
2980  struct is_nothrow_swappable_with
2981  : public __is_nothrow_swappable_with_impl<_Tp, _Up>::type
2982  {
2983  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2984  "first template argument must be a complete class or an unbounded array");
2985  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2986  "second template argument must be a complete class or an unbounded array");
2987  };
2988 
2989 #if __cplusplus >= 201402L
2990  /// is_swappable_with_v
2991  template<typename _Tp, typename _Up>
2992  _GLIBCXX17_INLINE constexpr bool is_swappable_with_v =
2993  is_swappable_with<_Tp, _Up>::value;
2994 
2995  /// is_nothrow_swappable_with_v
2996  template<typename _Tp, typename _Up>
2997  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_with_v =
2998  is_nothrow_swappable_with<_Tp, _Up>::value;
2999 #endif // __cplusplus >= 201402L
3000 
3001 #endif // __cpp_lib_is_swappable
3002 
3003  /// @cond undocumented
3004 
3005  // __is_invocable (std::is_invocable for C++11)
3006 
3007  // The primary template is used for invalid INVOKE expressions.
3008  template<typename _Result, typename _Ret,
3009  bool = is_void<_Ret>::value, typename = void>
3010  struct __is_invocable_impl
3011  : false_type
3012  {
3013  using __nothrow_conv = false_type; // For is_nothrow_invocable_r
3014  };
3015 
3016  // Used for valid INVOKE and INVOKE<void> expressions.
3017  template<typename _Result, typename _Ret>
3018  struct __is_invocable_impl<_Result, _Ret,
3019  /* is_void<_Ret> = */ true,
3020  __void_t<typename _Result::type>>
3021  : true_type
3022  {
3023  using __nothrow_conv = true_type; // For is_nothrow_invocable_r
3024  };
3025 
3026 #pragma GCC diagnostic push
3027 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
3028  // Used for INVOKE<R> expressions to check the implicit conversion to R.
3029  template<typename _Result, typename _Ret>
3030  struct __is_invocable_impl<_Result, _Ret,
3031  /* is_void<_Ret> = */ false,
3032  __void_t<typename _Result::type>>
3033  {
3034  private:
3035  // The type of the INVOKE expression.
3036  using _Res_t = typename _Result::type;
3037 
3038  // Unlike declval, this doesn't add_rvalue_reference, so it respects
3039  // guaranteed copy elision.
3040  static _Res_t _S_get() noexcept;
3041 
3042  // Used to check if _Res_t can implicitly convert to _Tp.
3043  template<typename _Tp>
3044  static void _S_conv(__type_identity_t<_Tp>) noexcept;
3045 
3046  // This overload is viable if INVOKE(f, args...) can convert to _Tp.
3047  template<typename _Tp,
3048  bool _Nothrow = noexcept(_S_conv<_Tp>(_S_get())),
3049  typename = decltype(_S_conv<_Tp>(_S_get())),
3050 #if __has_builtin(__reference_converts_from_temporary)
3051  bool _Dangle = __reference_converts_from_temporary(_Tp, _Res_t)
3052 #else
3053  bool _Dangle = false
3054 #endif
3055  >
3056  static __bool_constant<_Nothrow && !_Dangle>
3057  _S_test(int);
3058 
3059  template<typename _Tp, bool = false>
3060  static false_type
3061  _S_test(...);
3062 
3063  public:
3064  // For is_invocable_r
3065  using type = decltype(_S_test<_Ret, /* Nothrow = */ true>(1));
3066 
3067  // For is_nothrow_invocable_r
3068  using __nothrow_conv = decltype(_S_test<_Ret>(1));
3069  };
3070 #pragma GCC diagnostic pop
3071 
3072  template<typename _Fn, typename... _ArgTypes>
3073  struct __is_invocable
3074  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
3075  { };
3076 
3077  template<typename _Fn, typename _Tp, typename... _Args>
3078  constexpr bool __call_is_nt(__invoke_memfun_ref)
3079  {
3080  using _Up = typename __inv_unwrap<_Tp>::type;
3081  return noexcept((std::declval<_Up>().*std::declval<_Fn>())(
3082  std::declval<_Args>()...));
3083  }
3084 
3085  template<typename _Fn, typename _Tp, typename... _Args>
3086  constexpr bool __call_is_nt(__invoke_memfun_deref)
3087  {
3088  return noexcept(((*std::declval<_Tp>()).*std::declval<_Fn>())(
3089  std::declval<_Args>()...));
3090  }
3091 
3092  template<typename _Fn, typename _Tp>
3093  constexpr bool __call_is_nt(__invoke_memobj_ref)
3094  {
3095  using _Up = typename __inv_unwrap<_Tp>::type;
3096  return noexcept(std::declval<_Up>().*std::declval<_Fn>());
3097  }
3098 
3099  template<typename _Fn, typename _Tp>
3100  constexpr bool __call_is_nt(__invoke_memobj_deref)
3101  {
3102  return noexcept((*std::declval<_Tp>()).*std::declval<_Fn>());
3103  }
3104 
3105  template<typename _Fn, typename... _Args>
3106  constexpr bool __call_is_nt(__invoke_other)
3107  {
3108  return noexcept(std::declval<_Fn>()(std::declval<_Args>()...));
3109  }
3110 
3111  template<typename _Result, typename _Fn, typename... _Args>
3112  struct __call_is_nothrow
3113  : __bool_constant<
3114  std::__call_is_nt<_Fn, _Args...>(typename _Result::__invoke_type{})
3115  >
3116  { };
3117 
3118  template<typename _Fn, typename... _Args>
3119  using __call_is_nothrow_
3120  = __call_is_nothrow<__invoke_result<_Fn, _Args...>, _Fn, _Args...>;
3121 
3122  // __is_nothrow_invocable (std::is_nothrow_invocable for C++11)
3123  template<typename _Fn, typename... _Args>
3124  struct __is_nothrow_invocable
3125  : __and_<__is_invocable<_Fn, _Args...>,
3126  __call_is_nothrow_<_Fn, _Args...>>::type
3127  { };
3128 
3129 #pragma GCC diagnostic push
3130 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
3131  struct __nonesuchbase {};
3132  struct __nonesuch : private __nonesuchbase {
3133  ~__nonesuch() = delete;
3134  __nonesuch(__nonesuch const&) = delete;
3135  void operator=(__nonesuch const&) = delete;
3136  };
3137 #pragma GCC diagnostic pop
3138  /// @endcond
3139 
3140 #ifdef __cpp_lib_is_invocable // C++ >= 17
3141  /// std::invoke_result
3142  template<typename _Functor, typename... _ArgTypes>
3143  struct invoke_result
3144  : public __invoke_result<_Functor, _ArgTypes...>
3145  {
3146  static_assert(std::__is_complete_or_unbounded(__type_identity<_Functor>{}),
3147  "_Functor must be a complete class or an unbounded array");
3148  static_assert((std::__is_complete_or_unbounded(
3149  __type_identity<_ArgTypes>{}) && ...),
3150  "each argument type must be a complete class or an unbounded array");
3151  };
3152 
3153  /// std::invoke_result_t
3154  template<typename _Fn, typename... _Args>
3155  using invoke_result_t = typename invoke_result<_Fn, _Args...>::type;
3156 
3157  /// std::is_invocable
3158  template<typename _Fn, typename... _ArgTypes>
3159  struct is_invocable
3160  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
3161  {
3162  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3163  "_Fn must be a complete class or an unbounded array");
3164  static_assert((std::__is_complete_or_unbounded(
3165  __type_identity<_ArgTypes>{}) && ...),
3166  "each argument type must be a complete class or an unbounded array");
3167  };
3168 
3169  /// std::is_invocable_r
3170  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3171  struct is_invocable_r
3172  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>::type
3173  {
3174  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3175  "_Fn must be a complete class or an unbounded array");
3176  static_assert((std::__is_complete_or_unbounded(
3177  __type_identity<_ArgTypes>{}) && ...),
3178  "each argument type must be a complete class or an unbounded array");
3179  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3180  "_Ret must be a complete class or an unbounded array");
3181  };
3182 
3183  /// std::is_nothrow_invocable
3184  template<typename _Fn, typename... _ArgTypes>
3185  struct is_nothrow_invocable
3186  : __and_<__is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>,
3187  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3188  {
3189  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3190  "_Fn must be a complete class or an unbounded array");
3191  static_assert((std::__is_complete_or_unbounded(
3192  __type_identity<_ArgTypes>{}) && ...),
3193  "each argument type must be a complete class or an unbounded array");
3194  };
3195 
3196  /// @cond undocumented
3197  // This checks that the INVOKE<R> expression is well-formed and that the
3198  // conversion to R does not throw. It does *not* check whether the INVOKE
3199  // expression itself can throw. That is done by __call_is_nothrow_ instead.
3200  template<typename _Result, typename _Ret>
3201  using __is_nt_invocable_impl
3202  = typename __is_invocable_impl<_Result, _Ret>::__nothrow_conv;
3203  /// @endcond
3204 
3205  /// std::is_nothrow_invocable_r
3206  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3207  struct is_nothrow_invocable_r
3208  : __and_<__is_nt_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>,
3209  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3210  {
3211  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3212  "_Fn must be a complete class or an unbounded array");
3213  static_assert((std::__is_complete_or_unbounded(
3214  __type_identity<_ArgTypes>{}) && ...),
3215  "each argument type must be a complete class or an unbounded array");
3216  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3217  "_Ret must be a complete class or an unbounded array");
3218  };
3219 #endif // __cpp_lib_is_invocable
3220 
3221 #if __cpp_lib_type_trait_variable_templates // C++ >= 17
3222  /**
3223  * @defgroup variable_templates Variable templates for type traits
3224  * @ingroup metaprogramming
3225  *
3226  * Each variable `is_xxx_v<T>` is a boolean constant with the same value
3227  * as the `value` member of the corresponding type trait `is_xxx<T>`.
3228  *
3229  * @since C++17 unless noted otherwise.
3230  */
3231 
3232  /**
3233  * @{
3234  * @ingroup variable_templates
3235  */
3236 template <typename _Tp>
3237  inline constexpr bool is_void_v = is_void<_Tp>::value;
3238 template <typename _Tp>
3239  inline constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value;
3240 template <typename _Tp>
3241  inline constexpr bool is_integral_v = is_integral<_Tp>::value;
3242 template <typename _Tp>
3243  inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
3244 
3245 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_array)
3246 template <typename _Tp>
3247  inline constexpr bool is_array_v = __is_array(_Tp);
3248 #else
3249 template <typename _Tp>
3250  inline constexpr bool is_array_v = false;
3251 template <typename _Tp>
3252  inline constexpr bool is_array_v<_Tp[]> = true;
3253 template <typename _Tp, size_t _Num>
3254  inline constexpr bool is_array_v<_Tp[_Num]> = true;
3255 #endif
3256 
3257 template <typename _Tp>
3258  inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
3259 template <typename _Tp>
3260  inline constexpr bool is_lvalue_reference_v = false;
3261 template <typename _Tp>
3262  inline constexpr bool is_lvalue_reference_v<_Tp&> = true;
3263 template <typename _Tp>
3264  inline constexpr bool is_rvalue_reference_v = false;
3265 template <typename _Tp>
3266  inline constexpr bool is_rvalue_reference_v<_Tp&&> = true;
3267 
3268 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_object_pointer)
3269 template <typename _Tp>
3270  inline constexpr bool is_member_object_pointer_v =
3271  __is_member_object_pointer(_Tp);
3272 #else
3273 template <typename _Tp>
3274  inline constexpr bool is_member_object_pointer_v =
3275  is_member_object_pointer<_Tp>::value;
3276 #endif
3277 
3278 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_function_pointer)
3279 template <typename _Tp>
3280  inline constexpr bool is_member_function_pointer_v =
3281  __is_member_function_pointer(_Tp);
3282 #else
3283 template <typename _Tp>
3284  inline constexpr bool is_member_function_pointer_v =
3285  is_member_function_pointer<_Tp>::value;
3286 #endif
3287 
3288 template <typename _Tp>
3289  inline constexpr bool is_enum_v = __is_enum(_Tp);
3290 template <typename _Tp>
3291  inline constexpr bool is_union_v = __is_union(_Tp);
3292 template <typename _Tp>
3293  inline constexpr bool is_class_v = __is_class(_Tp);
3294 // is_function_v is defined below, after is_const_v.
3295 
3296 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_reference)
3297 template <typename _Tp>
3298  inline constexpr bool is_reference_v = __is_reference(_Tp);
3299 #else
3300 template <typename _Tp>
3301  inline constexpr bool is_reference_v = false;
3302 template <typename _Tp>
3303  inline constexpr bool is_reference_v<_Tp&> = true;
3304 template <typename _Tp>
3305  inline constexpr bool is_reference_v<_Tp&&> = true;
3306 #endif
3307 
3308 template <typename _Tp>
3309  inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
3310 template <typename _Tp>
3311  inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
3312 
3313 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_object)
3314 template <typename _Tp>
3315  inline constexpr bool is_object_v = __is_object(_Tp);
3316 #else
3317 template <typename _Tp>
3318  inline constexpr bool is_object_v = is_object<_Tp>::value;
3319 #endif
3320 
3321 template <typename _Tp>
3322  inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
3323 template <typename _Tp>
3324  inline constexpr bool is_compound_v = !is_fundamental_v<_Tp>;
3325 
3326 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_pointer)
3327 template <typename _Tp>
3328  inline constexpr bool is_member_pointer_v = __is_member_pointer(_Tp);
3329 #else
3330 template <typename _Tp>
3331  inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
3332 #endif
3333 
3334 template <typename _Tp>
3335  inline constexpr bool is_const_v = false;
3336 template <typename _Tp>
3337  inline constexpr bool is_const_v<const _Tp> = true;
3338 
3339 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function)
3340 template <typename _Tp>
3341  inline constexpr bool is_function_v = __is_function(_Tp);
3342 #else
3343 template <typename _Tp>
3344  inline constexpr bool is_function_v = !is_const_v<const _Tp>;
3345 template <typename _Tp>
3346  inline constexpr bool is_function_v<_Tp&> = false;
3347 template <typename _Tp>
3348  inline constexpr bool is_function_v<_Tp&&> = false;
3349 #endif
3350 
3351 template <typename _Tp>
3352  inline constexpr bool is_volatile_v = false;
3353 template <typename _Tp>
3354  inline constexpr bool is_volatile_v<volatile _Tp> = true;
3355 
3356 template <typename _Tp>
3357  inline constexpr bool is_trivial_v = __is_trivial(_Tp);
3358 template <typename _Tp>
3359  inline constexpr bool is_trivially_copyable_v = __is_trivially_copyable(_Tp);
3360 template <typename _Tp>
3361  inline constexpr bool is_standard_layout_v = __is_standard_layout(_Tp);
3362 template <typename _Tp>
3363  _GLIBCXX20_DEPRECATED_SUGGEST("is_standard_layout_v && is_trivial_v")
3364  inline constexpr bool is_pod_v = __is_pod(_Tp);
3365 template <typename _Tp>
3366  _GLIBCXX17_DEPRECATED
3367  inline constexpr bool is_literal_type_v = __is_literal_type(_Tp);
3368 template <typename _Tp>
3369  inline constexpr bool is_empty_v = __is_empty(_Tp);
3370 template <typename _Tp>
3371  inline constexpr bool is_polymorphic_v = __is_polymorphic(_Tp);
3372 template <typename _Tp>
3373  inline constexpr bool is_abstract_v = __is_abstract(_Tp);
3374 template <typename _Tp>
3375  inline constexpr bool is_final_v = __is_final(_Tp);
3376 
3377 template <typename _Tp>
3378  inline constexpr bool is_signed_v = is_signed<_Tp>::value;
3379 template <typename _Tp>
3380  inline constexpr bool is_unsigned_v = is_unsigned<_Tp>::value;
3381 
3382 template <typename _Tp, typename... _Args>
3383  inline constexpr bool is_constructible_v = __is_constructible(_Tp, _Args...);
3384 template <typename _Tp>
3385  inline constexpr bool is_default_constructible_v = __is_constructible(_Tp);
3386 template <typename _Tp>
3387  inline constexpr bool is_copy_constructible_v
3388  = __is_constructible(_Tp, __add_lval_ref_t<const _Tp>);
3389 template <typename _Tp>
3390  inline constexpr bool is_move_constructible_v
3391  = __is_constructible(_Tp, __add_rval_ref_t<_Tp>);
3392 
3393 template <typename _Tp, typename _Up>
3394  inline constexpr bool is_assignable_v = __is_assignable(_Tp, _Up);
3395 template <typename _Tp>
3396  inline constexpr bool is_copy_assignable_v
3397  = __is_assignable(__add_lval_ref_t<_Tp>, __add_lval_ref_t<const _Tp>);
3398 template <typename _Tp>
3399  inline constexpr bool is_move_assignable_v
3400  = __is_assignable(__add_lval_ref_t<_Tp>, __add_rval_ref_t<_Tp>);
3401 
3402 template <typename _Tp>
3403  inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
3404 
3405 template <typename _Tp, typename... _Args>
3406  inline constexpr bool is_trivially_constructible_v
3407  = __is_trivially_constructible(_Tp, _Args...);
3408 template <typename _Tp>
3409  inline constexpr bool is_trivially_default_constructible_v
3410  = __is_trivially_constructible(_Tp);
3411 template <typename _Tp>
3412  inline constexpr bool is_trivially_copy_constructible_v
3413  = __is_trivially_constructible(_Tp, __add_lval_ref_t<const _Tp>);
3414 template <typename _Tp>
3415  inline constexpr bool is_trivially_move_constructible_v
3416  = __is_trivially_constructible(_Tp, __add_rval_ref_t<_Tp>);
3417 
3418 template <typename _Tp, typename _Up>
3419  inline constexpr bool is_trivially_assignable_v
3420  = __is_trivially_assignable(_Tp, _Up);
3421 template <typename _Tp>
3422  inline constexpr bool is_trivially_copy_assignable_v
3423  = __is_trivially_assignable(__add_lval_ref_t<_Tp>,
3424  __add_lval_ref_t<const _Tp>);
3425 template <typename _Tp>
3426  inline constexpr bool is_trivially_move_assignable_v
3427  = __is_trivially_assignable(__add_lval_ref_t<_Tp>,
3428  __add_rval_ref_t<_Tp>);
3429 
3430 #if __cpp_concepts
3431 template <typename _Tp>
3432  inline constexpr bool is_trivially_destructible_v = false;
3433 
3434 template <typename _Tp>
3435  requires (!is_reference_v<_Tp>) && requires (_Tp& __t) { __t.~_Tp(); }
3436  inline constexpr bool is_trivially_destructible_v<_Tp>
3437  = __has_trivial_destructor(_Tp);
3438 template <typename _Tp>
3439  inline constexpr bool is_trivially_destructible_v<_Tp&> = true;
3440 template <typename _Tp>
3441  inline constexpr bool is_trivially_destructible_v<_Tp&&> = true;
3442 template <typename _Tp, size_t _Nm>
3443  inline constexpr bool is_trivially_destructible_v<_Tp[_Nm]>
3444  = is_trivially_destructible_v<_Tp>;
3445 #else
3446 template <typename _Tp>
3447  inline constexpr bool is_trivially_destructible_v =
3448  is_trivially_destructible<_Tp>::value;
3449 #endif
3450 
3451 template <typename _Tp, typename... _Args>
3452  inline constexpr bool is_nothrow_constructible_v
3453  = __is_nothrow_constructible(_Tp, _Args...);
3454 template <typename _Tp>
3455  inline constexpr bool is_nothrow_default_constructible_v
3456  = __is_nothrow_constructible(_Tp);
3457 template <typename _Tp>
3458  inline constexpr bool is_nothrow_copy_constructible_v
3459  = __is_nothrow_constructible(_Tp, __add_lval_ref_t<const _Tp>);
3460 template <typename _Tp>
3461  inline constexpr bool is_nothrow_move_constructible_v
3462  = __is_nothrow_constructible(_Tp, __add_rval_ref_t<_Tp>);
3463 
3464 template <typename _Tp, typename _Up>
3465  inline constexpr bool is_nothrow_assignable_v
3466  = __is_nothrow_assignable(_Tp, _Up);
3467 template <typename _Tp>
3468  inline constexpr bool is_nothrow_copy_assignable_v
3469  = __is_nothrow_assignable(__add_lval_ref_t<_Tp>,
3470  __add_lval_ref_t<const _Tp>);
3471 template <typename _Tp>
3472  inline constexpr bool is_nothrow_move_assignable_v
3473  = __is_nothrow_assignable(__add_lval_ref_t<_Tp>, __add_rval_ref_t<_Tp>);
3474 
3475 template <typename _Tp>
3476  inline constexpr bool is_nothrow_destructible_v =
3477  is_nothrow_destructible<_Tp>::value;
3478 
3479 template <typename _Tp>
3480  inline constexpr bool has_virtual_destructor_v
3481  = __has_virtual_destructor(_Tp);
3482 
3483 template <typename _Tp>
3484  inline constexpr size_t alignment_of_v = alignment_of<_Tp>::value;
3485 
3486 template <typename _Tp>
3487  inline constexpr size_t rank_v = 0;
3488 template <typename _Tp, size_t _Size>
3489  inline constexpr size_t rank_v<_Tp[_Size]> = 1 + rank_v<_Tp>;
3490 template <typename _Tp>
3491  inline constexpr size_t rank_v<_Tp[]> = 1 + rank_v<_Tp>;
3492 
3493 template <typename _Tp, unsigned _Idx = 0>
3494  inline constexpr size_t extent_v = 0;
3495 template <typename _Tp, size_t _Size>
3496  inline constexpr size_t extent_v<_Tp[_Size], 0> = _Size;
3497 template <typename _Tp, unsigned _Idx, size_t _Size>
3498  inline constexpr size_t extent_v<_Tp[_Size], _Idx> = extent_v<_Tp, _Idx - 1>;
3499 template <typename _Tp>
3500  inline constexpr size_t extent_v<_Tp[], 0> = 0;
3501 template <typename _Tp, unsigned _Idx>
3502  inline constexpr size_t extent_v<_Tp[], _Idx> = extent_v<_Tp, _Idx - 1>;
3503 
3504 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_same)
3505 template <typename _Tp, typename _Up>
3506  inline constexpr bool is_same_v = __is_same(_Tp, _Up);
3507 #else
3508 template <typename _Tp, typename _Up>
3509  inline constexpr bool is_same_v = false;
3510 template <typename _Tp>
3511  inline constexpr bool is_same_v<_Tp, _Tp> = true;
3512 #endif
3513 template <typename _Base, typename _Derived>
3514  inline constexpr bool is_base_of_v = __is_base_of(_Base, _Derived);
3515 #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_convertible)
3516 template <typename _From, typename _To>
3517  inline constexpr bool is_convertible_v = __is_convertible(_From, _To);
3518 #else
3519 template <typename _From, typename _To>
3520  inline constexpr bool is_convertible_v = is_convertible<_From, _To>::value;
3521 #endif
3522 template<typename _Fn, typename... _Args>
3523  inline constexpr bool is_invocable_v = is_invocable<_Fn, _Args...>::value;
3524 template<typename _Fn, typename... _Args>
3525  inline constexpr bool is_nothrow_invocable_v
3526  = is_nothrow_invocable<_Fn, _Args...>::value;
3527 template<typename _Ret, typename _Fn, typename... _Args>
3528  inline constexpr bool is_invocable_r_v
3529  = is_invocable_r<_Ret, _Fn, _Args...>::value;
3530 template<typename _Ret, typename _Fn, typename... _Args>
3531  inline constexpr bool is_nothrow_invocable_r_v
3532  = is_nothrow_invocable_r<_Ret, _Fn, _Args...>::value;
3533 /// @}
3534 #endif // __cpp_lib_type_trait_variable_templates
3535 
3536 #ifdef __cpp_lib_has_unique_object_representations // C++ >= 17 && HAS_UNIQ_OBJ_REP
3537  /// has_unique_object_representations
3538  /// @since C++17
3539  template<typename _Tp>
3540  struct has_unique_object_representations
3541  : bool_constant<__has_unique_object_representations(
3542  remove_cv_t<remove_all_extents_t<_Tp>>
3543  )>
3544  {
3545  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
3546  "template argument must be a complete class or an unbounded array");
3547  };
3548 
3549 # if __cpp_lib_type_trait_variable_templates // C++ >= 17
3550  /// @ingroup variable_templates
3551  template<typename _Tp>
3552  inline constexpr bool has_unique_object_representations_v
3553  = has_unique_object_representations<_Tp>::value;
3554 # endif
3555 #endif
3556 
3557 #ifdef __cpp_lib_is_aggregate // C++ >= 17 && builtin_is_aggregate
3558  /// is_aggregate - true if the type is an aggregate.
3559  /// @since C++17
3560  template<typename _Tp>
3561  struct is_aggregate
3562  : bool_constant<__is_aggregate(remove_cv_t<_Tp>)>
3563  { };
3564 
3565 # if __cpp_lib_type_trait_variable_templates // C++ >= 17
3566  /** is_aggregate_v - true if the type is an aggregate.
3567  * @ingroup variable_templates
3568  * @since C++17
3569  */
3570  template<typename _Tp>
3571  inline constexpr bool is_aggregate_v = __is_aggregate(remove_cv_t<_Tp>);
3572 # endif
3573 #endif
3574 
3575  /** * Remove references and cv-qualifiers.
3576  * @since C++20
3577  * @{
3578  */
3579 #ifdef __cpp_lib_remove_cvref // C++ >= 20
3580 # if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_cvref)
3581  template<typename _Tp>
3582  struct remove_cvref
3583  { using type = __remove_cvref(_Tp); };
3584 # else
3585  template<typename _Tp>
3586  struct remove_cvref
3587  { using type = typename remove_cv<_Tp>::type; };
3588 
3589  template<typename _Tp>
3590  struct remove_cvref<_Tp&>
3591  { using type = typename remove_cv<_Tp>::type; };
3592 
3593  template<typename _Tp>
3594  struct remove_cvref<_Tp&&>
3595  { using type = typename remove_cv<_Tp>::type; };
3596 # endif
3597 
3598  template<typename _Tp>
3599  using remove_cvref_t = typename remove_cvref<_Tp>::type;
3600  /// @}
3601 #endif // __cpp_lib_remove_cvref
3602 
3603 #ifdef __cpp_lib_type_identity // C++ >= 20
3604  /** * Identity metafunction.
3605  * @since C++20
3606  * @{
3607  */
3608  template<typename _Tp>
3609  struct type_identity { using type = _Tp; };
3610 
3611  template<typename _Tp>
3612  using type_identity_t = typename type_identity<_Tp>::type;
3613  /// @}
3614 #endif
3615 
3616 #ifdef __cpp_lib_unwrap_ref // C++ >= 20
3617  /** Unwrap a reference_wrapper
3618  * @since C++20
3619  * @{
3620  */
3621  template<typename _Tp>
3622  struct unwrap_reference { using type = _Tp; };
3623 
3624  template<typename _Tp>
3625  struct unwrap_reference<reference_wrapper<_Tp>> { using type = _Tp&; };
3626 
3627  template<typename _Tp>
3628  using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
3629  /// @}
3630 
3631  /** Decay type and if it's a reference_wrapper, unwrap it
3632  * @since C++20
3633  * @{
3634  */
3635  template<typename _Tp>
3636  struct unwrap_ref_decay { using type = unwrap_reference_t<decay_t<_Tp>>; };
3637 
3638  template<typename _Tp>
3639  using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
3640  /// @}
3641 #endif // __cpp_lib_unwrap_ref
3642 
3643 #ifdef __cpp_lib_bounded_array_traits // C++ >= 20
3644  /// True for a type that is an array of known bound.
3645  /// @ingroup variable_templates
3646  /// @since C++20
3647 # if _GLIBCXX_USE_BUILTIN_TRAIT(__is_bounded_array)
3648  template<typename _Tp>
3649  inline constexpr bool is_bounded_array_v = __is_bounded_array(_Tp);
3650 # else
3651  template<typename _Tp>
3652  inline constexpr bool is_bounded_array_v = false;
3653 
3654  template<typename _Tp, size_t _Size>
3655  inline constexpr bool is_bounded_array_v<_Tp[_Size]> = true;
3656 # endif
3657 
3658  /// True for a type that is an array of unknown bound.
3659  /// @ingroup variable_templates
3660  /// @since C++20
3661  template<typename _Tp>
3662  inline constexpr bool is_unbounded_array_v = false;
3663 
3664  template<typename _Tp>
3665  inline constexpr bool is_unbounded_array_v<_Tp[]> = true;
3666 
3667  /// True for a type that is an array of known bound.
3668  /// @since C++20
3669  template<typename _Tp>
3670  struct is_bounded_array
3671  : public bool_constant<is_bounded_array_v<_Tp>>
3672  { };
3673 
3674  /// True for a type that is an array of unknown bound.
3675  /// @since C++20
3676  template<typename _Tp>
3677  struct is_unbounded_array
3678  : public bool_constant<is_unbounded_array_v<_Tp>>
3679  { };
3680 #endif // __cpp_lib_bounded_array_traits
3681 
3682 #if __has_builtin(__is_layout_compatible) && __cplusplus >= 202002L
3683 
3684  /// @since C++20
3685  template<typename _Tp, typename _Up>
3686  struct is_layout_compatible
3687  : bool_constant<__is_layout_compatible(_Tp, _Up)>
3688  { };
3689 
3690  /// @ingroup variable_templates
3691  /// @since C++20
3692  template<typename _Tp, typename _Up>
3693  constexpr bool is_layout_compatible_v
3694  = __is_layout_compatible(_Tp, _Up);
3695 
3696 #if __has_builtin(__builtin_is_corresponding_member)
3697 # ifndef __cpp_lib_is_layout_compatible
3698 # error "libstdc++ bug: is_corresponding_member and is_layout_compatible are provided but their FTM is not set"
3699 # endif
3700 
3701  /// @since C++20
3702  template<typename _S1, typename _S2, typename _M1, typename _M2>
3703  constexpr bool
3704  is_corresponding_member(_M1 _S1::*__m1, _M2 _S2::*__m2) noexcept
3705  { return __builtin_is_corresponding_member(__m1, __m2); }
3706 #endif
3707 #endif
3708 
3709 #if __has_builtin(__is_pointer_interconvertible_base_of) \
3710  && __cplusplus >= 202002L
3711  /// True if `_Derived` is standard-layout and has a base class of type `_Base`
3712  /// @since C++20
3713  template<typename _Base, typename _Derived>
3714  struct is_pointer_interconvertible_base_of
3715  : bool_constant<__is_pointer_interconvertible_base_of(_Base, _Derived)>
3716  { };
3717 
3718  /// @ingroup variable_templates
3719  /// @since C++20
3720  template<typename _Base, typename _Derived>
3721  constexpr bool is_pointer_interconvertible_base_of_v
3722  = __is_pointer_interconvertible_base_of(_Base, _Derived);
3723 
3724 #if __has_builtin(__builtin_is_pointer_interconvertible_with_class)
3725 # ifndef __cpp_lib_is_pointer_interconvertible
3726 # error "libstdc++ bug: is_pointer_interconvertible available but FTM is not set"
3727 # endif
3728 
3729  /// True if `__mp` points to the first member of a standard-layout type
3730  /// @returns true if `s.*__mp` is pointer-interconvertible with `s`
3731  /// @since C++20
3732  template<typename _Tp, typename _Mem>
3733  constexpr bool
3734  is_pointer_interconvertible_with_class(_Mem _Tp::*__mp) noexcept
3735  { return __builtin_is_pointer_interconvertible_with_class(__mp); }
3736 #endif
3737 #endif
3738 
3739 #ifdef __cpp_lib_is_scoped_enum // C++ >= 23
3740  /// True if the type is a scoped enumeration type.
3741  /// @since C++23
3742 
3743 # if _GLIBCXX_USE_BUILTIN_TRAIT(__is_scoped_enum)
3744  template<typename _Tp>
3745  struct is_scoped_enum
3746  : bool_constant<__is_scoped_enum(_Tp)>
3747  { };
3748 # else
3749  template<typename _Tp>
3750  struct is_scoped_enum
3751  : false_type
3752  { };
3753 
3754  template<typename _Tp>
3755  requires __is_enum(_Tp)
3756  && requires(remove_cv_t<_Tp> __t) { __t = __t; } // fails if incomplete
3757  struct is_scoped_enum<_Tp>
3758  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3759  { };
3760 # endif
3761 
3762  /// @ingroup variable_templates
3763  /// @since C++23
3764 # if _GLIBCXX_USE_BUILTIN_TRAIT(__is_scoped_enum)
3765  template<typename _Tp>
3766  inline constexpr bool is_scoped_enum_v = __is_scoped_enum(_Tp);
3767 # else
3768  template<typename _Tp>
3769  inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
3770 # endif
3771 #endif
3772 
3773 #ifdef __cpp_lib_reference_from_temporary // C++ >= 23 && ref_{converts,constructs}_from_temp
3774  /// True if _Tp is a reference type, a _Up value can be bound to _Tp in
3775  /// direct-initialization, and a temporary object would be bound to
3776  /// the reference, false otherwise.
3777  /// @since C++23
3778  template<typename _Tp, typename _Up>
3779  struct reference_constructs_from_temporary
3780  : public bool_constant<__reference_constructs_from_temporary(_Tp, _Up)>
3781  {
3782  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{})
3783  && std::__is_complete_or_unbounded(__type_identity<_Up>{}),
3784  "template argument must be a complete class or an unbounded array");
3785  };
3786 
3787  /// True if _Tp is a reference type, a _Up value can be bound to _Tp in
3788  /// copy-initialization, and a temporary object would be bound to
3789  /// the reference, false otherwise.
3790  /// @since C++23
3791  template<typename _Tp, typename _Up>
3792  struct reference_converts_from_temporary
3793  : public bool_constant<__reference_converts_from_temporary(_Tp, _Up)>
3794  {
3795  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{})
3796  && std::__is_complete_or_unbounded(__type_identity<_Up>{}),
3797  "template argument must be a complete class or an unbounded array");
3798  };
3799 
3800  /// @ingroup variable_templates
3801  /// @since C++23
3802  template<typename _Tp, typename _Up>
3803  inline constexpr bool reference_constructs_from_temporary_v
3804  = reference_constructs_from_temporary<_Tp, _Up>::value;
3805 
3806  /// @ingroup variable_templates
3807  /// @since C++23
3808  template<typename _Tp, typename _Up>
3809  inline constexpr bool reference_converts_from_temporary_v
3810  = reference_converts_from_temporary<_Tp, _Up>::value;
3811 #endif // __cpp_lib_reference_from_temporary
3812 
3813 #ifdef __cpp_lib_is_constant_evaluated // C++ >= 20 && HAVE_IS_CONST_EVAL
3814  /// Returns true only when called during constant evaluation.
3815  /// @since C++20
3816  constexpr inline bool
3817  is_constant_evaluated() noexcept
3818  {
3819 #if __cpp_if_consteval >= 202106L
3820  if consteval { return true; } else { return false; }
3821 #else
3822  return __builtin_is_constant_evaluated();
3823 #endif
3824  }
3825 #endif
3826 
3827 #if __cplusplus >= 202002L
3828  /// @cond undocumented
3829  template<typename _From, typename _To>
3830  using __copy_cv = typename __match_cv_qualifiers<_From, _To>::__type;
3831 
3832  template<typename _Xp, typename _Yp>
3833  using __cond_res
3834  = decltype(false ? declval<_Xp(&)()>()() : declval<_Yp(&)()>()());
3835 
3836  template<typename _Ap, typename _Bp, typename = void>
3837  struct __common_ref_impl
3838  { };
3839 
3840  // [meta.trans.other], COMMON-REF(A, B)
3841  template<typename _Ap, typename _Bp>
3842  using __common_ref = typename __common_ref_impl<_Ap, _Bp>::type;
3843 
3844  // COND-RES(COPYCV(X, Y) &, COPYCV(Y, X) &)
3845  template<typename _Xp, typename _Yp>
3846  using __condres_cvref
3847  = __cond_res<__copy_cv<_Xp, _Yp>&, __copy_cv<_Yp, _Xp>&>;
3848 
3849  // If A and B are both lvalue reference types, ...
3850  template<typename _Xp, typename _Yp>
3851  struct __common_ref_impl<_Xp&, _Yp&, __void_t<__condres_cvref<_Xp, _Yp>>>
3852  : enable_if<is_reference_v<__condres_cvref<_Xp, _Yp>>,
3853  __condres_cvref<_Xp, _Yp>>
3854  { };
3855 
3856  // let C be remove_reference_t<COMMON-REF(X&, Y&)>&&
3857  template<typename _Xp, typename _Yp>
3858  using __common_ref_C = remove_reference_t<__common_ref<_Xp&, _Yp&>>&&;
3859 
3860  // If A and B are both rvalue reference types, ...
3861  template<typename _Xp, typename _Yp>
3862  struct __common_ref_impl<_Xp&&, _Yp&&,
3863  _Require<is_convertible<_Xp&&, __common_ref_C<_Xp, _Yp>>,
3864  is_convertible<_Yp&&, __common_ref_C<_Xp, _Yp>>>>
3865  { using type = __common_ref_C<_Xp, _Yp>; };
3866 
3867  // let D be COMMON-REF(const X&, Y&)
3868  template<typename _Xp, typename _Yp>
3869  using __common_ref_D = __common_ref<const _Xp&, _Yp&>;
3870 
3871  // If A is an rvalue reference and B is an lvalue reference, ...
3872  template<typename _Xp, typename _Yp>
3873  struct __common_ref_impl<_Xp&&, _Yp&,
3874  _Require<is_convertible<_Xp&&, __common_ref_D<_Xp, _Yp>>>>
3875  { using type = __common_ref_D<_Xp, _Yp>; };
3876 
3877  // If A is an lvalue reference and B is an rvalue reference, ...
3878  template<typename _Xp, typename _Yp>
3879  struct __common_ref_impl<_Xp&, _Yp&&>
3880  : __common_ref_impl<_Yp&&, _Xp&>
3881  { };
3882  /// @endcond
3883 
3884  template<typename _Tp, typename _Up,
3885  template<typename> class _TQual, template<typename> class _UQual>
3886  struct basic_common_reference
3887  { };
3888 
3889  /// @cond undocumented
3890  template<typename _Tp>
3891  struct __xref
3892  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>; };
3893 
3894  template<typename _Tp>
3895  struct __xref<_Tp&>
3896  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&; };
3897 
3898  template<typename _Tp>
3899  struct __xref<_Tp&&>
3900  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&&; };
3901 
3902  template<typename _Tp1, typename _Tp2>
3903  using __basic_common_ref
3904  = typename basic_common_reference<remove_cvref_t<_Tp1>,
3905  remove_cvref_t<_Tp2>,
3906  __xref<_Tp1>::template __type,
3907  __xref<_Tp2>::template __type>::type;
3908  /// @endcond
3909 
3910  template<typename... _Tp>
3911  struct common_reference;
3912 
3913  template<typename... _Tp>
3914  using common_reference_t = typename common_reference<_Tp...>::type;
3915 
3916  // If sizeof...(T) is zero, there shall be no member type.
3917  template<>
3918  struct common_reference<>
3919  { };
3920 
3921  // If sizeof...(T) is one ...
3922  template<typename _Tp0>
3923  struct common_reference<_Tp0>
3924  { using type = _Tp0; };
3925 
3926  /// @cond undocumented
3927  template<typename _Tp1, typename _Tp2, int _Bullet = 1, typename = void>
3928  struct __common_reference_impl
3929  : __common_reference_impl<_Tp1, _Tp2, _Bullet + 1>
3930  { };
3931 
3932  // If sizeof...(T) is two ...
3933  template<typename _Tp1, typename _Tp2>
3934  struct common_reference<_Tp1, _Tp2>
3935  : __common_reference_impl<_Tp1, _Tp2>
3936  { };
3937 
3938  // If T1 and T2 are reference types and COMMON-REF(T1, T2) is well-formed, ...
3939  template<typename _Tp1, typename _Tp2>
3940  struct __common_reference_impl<_Tp1&, _Tp2&, 1,
3941  void_t<__common_ref<_Tp1&, _Tp2&>>>
3942  { using type = __common_ref<_Tp1&, _Tp2&>; };
3943 
3944  template<typename _Tp1, typename _Tp2>
3945  struct __common_reference_impl<_Tp1&&, _Tp2&&, 1,
3946  void_t<__common_ref<_Tp1&&, _Tp2&&>>>
3947  { using type = __common_ref<_Tp1&&, _Tp2&&>; };
3948 
3949  template<typename _Tp1, typename _Tp2>
3950  struct __common_reference_impl<_Tp1&, _Tp2&&, 1,
3951  void_t<__common_ref<_Tp1&, _Tp2&&>>>
3952  { using type = __common_ref<_Tp1&, _Tp2&&>; };
3953 
3954  template<typename _Tp1, typename _Tp2>
3955  struct __common_reference_impl<_Tp1&&, _Tp2&, 1,
3956  void_t<__common_ref<_Tp1&&, _Tp2&>>>
3957  { using type = __common_ref<_Tp1&&, _Tp2&>; };
3958 
3959  // Otherwise, if basic_common_reference<...>::type is well-formed, ...
3960  template<typename _Tp1, typename _Tp2>
3961  struct __common_reference_impl<_Tp1, _Tp2, 2,
3962  void_t<__basic_common_ref<_Tp1, _Tp2>>>
3963  { using type = __basic_common_ref<_Tp1, _Tp2>; };
3964 
3965  // Otherwise, if COND-RES(T1, T2) is well-formed, ...
3966  template<typename _Tp1, typename _Tp2>
3967  struct __common_reference_impl<_Tp1, _Tp2, 3,
3968  void_t<__cond_res<_Tp1, _Tp2>>>
3969  { using type = __cond_res<_Tp1, _Tp2>; };
3970 
3971  // Otherwise, if common_type_t<T1, T2> is well-formed, ...
3972  template<typename _Tp1, typename _Tp2>
3973  struct __common_reference_impl<_Tp1, _Tp2, 4,
3974  void_t<common_type_t<_Tp1, _Tp2>>>
3975  { using type = common_type_t<_Tp1, _Tp2>; };
3976 
3977  // Otherwise, there shall be no member type.
3978  template<typename _Tp1, typename _Tp2>
3979  struct __common_reference_impl<_Tp1, _Tp2, 5, void>
3980  { };
3981 
3982  // Otherwise, if sizeof...(T) is greater than two, ...
3983  template<typename _Tp1, typename _Tp2, typename... _Rest>
3984  struct common_reference<_Tp1, _Tp2, _Rest...>
3985  : __common_type_fold<common_reference<_Tp1, _Tp2>,
3986  __common_type_pack<_Rest...>>
3987  { };
3988 
3989  // Reuse __common_type_fold for common_reference<T1, T2, Rest...>
3990  template<typename _Tp1, typename _Tp2, typename... _Rest>
3991  struct __common_type_fold<common_reference<_Tp1, _Tp2>,
3992  __common_type_pack<_Rest...>,
3993  void_t<common_reference_t<_Tp1, _Tp2>>>
3994  : public common_reference<common_reference_t<_Tp1, _Tp2>, _Rest...>
3995  { };
3996  /// @endcond
3997 
3998 #endif // C++2a
3999 
4000  /// @} group metaprogramming
4001 
4002 _GLIBCXX_END_NAMESPACE_VERSION
4003 } // namespace std
4004 
4005 #endif // C++11
4006 
4007 #endif // _GLIBCXX_TYPE_TRAITS