libstdc++
type_traits
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1 // C++11 <type_traits> -*- C++ -*-
2 
3 // Copyright (C) 2007-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file 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 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44  template<typename... _Elements>
45  class tuple;
46 
47  template<typename _Tp>
48  class reference_wrapper;
49 
50  /**
51  * @defgroup metaprogramming Metaprogramming
52  * @ingroup utilities
53  *
54  * Template utilities for compile-time introspection and modification,
55  * including type classification traits, type property inspection traits
56  * and type transformation traits.
57  *
58  * @since C++11
59  *
60  * @{
61  */
62 
63  /// integral_constant
64  template<typename _Tp, _Tp __v>
66  {
67  static constexpr _Tp value = __v;
68  typedef _Tp value_type;
70  constexpr operator value_type() const noexcept { return value; }
71 #if __cplusplus > 201103L
72 
73 #define __cpp_lib_integral_constant_callable 201304
74 
75  constexpr value_type operator()() const noexcept { return value; }
76 #endif
77  };
78 
79  template<typename _Tp, _Tp __v>
81 
82  /// The type used as a compile-time boolean with true value.
84 
85  /// The type used as a compile-time boolean with false value.
87 
88  /// @cond undocumented
89  /// bool_constant for C++11
90  template<bool __v>
91  using __bool_constant = integral_constant<bool, __v>;
92  /// @endcond
93 
94 #if __cplusplus >= 201703L
95 # define __cpp_lib_bool_constant 201505
96  /// Alias template for compile-time boolean constant types.
97  /// @since C++17
98  template<bool __v>
100 #endif
101 
102  // Metaprogramming helper types.
103 
104  template<bool, typename, typename>
105  struct conditional;
106 
107  /// @cond undocumented
108  template <typename _Type>
109  struct __type_identity
110  { using type = _Type; };
111 
112  template<typename _Tp>
113  using __type_identity_t = typename __type_identity<_Tp>::type;
114 
115  template<typename...>
116  struct __or_;
117 
118  template<>
119  struct __or_<>
120  : public false_type
121  { };
122 
123  template<typename _B1>
124  struct __or_<_B1>
125  : public _B1
126  { };
127 
128  template<typename _B1, typename _B2>
129  struct __or_<_B1, _B2>
130  : public conditional<_B1::value, _B1, _B2>::type
131  { };
132 
133  template<typename _B1, typename _B2, typename _B3, typename... _Bn>
134  struct __or_<_B1, _B2, _B3, _Bn...>
135  : public conditional<_B1::value, _B1, __or_<_B2, _B3, _Bn...>>::type
136  { };
137 
138  template<typename...>
139  struct __and_;
140 
141  template<>
142  struct __and_<>
143  : public true_type
144  { };
145 
146  template<typename _B1>
147  struct __and_<_B1>
148  : public _B1
149  { };
150 
151  template<typename _B1, typename _B2>
152  struct __and_<_B1, _B2>
153  : public conditional<_B1::value, _B2, _B1>::type
154  { };
155 
156  template<typename _B1, typename _B2, typename _B3, typename... _Bn>
157  struct __and_<_B1, _B2, _B3, _Bn...>
158  : public conditional<_B1::value, __and_<_B2, _B3, _Bn...>, _B1>::type
159  { };
160 
161  template<typename _Pp>
162  struct __not_
163  : public __bool_constant<!bool(_Pp::value)>
164  { };
165  /// @endcond
166 
167 #if __cplusplus >= 201703L
168 
169  /// @cond undocumented
170  template<typename... _Bn>
171  inline constexpr bool __or_v = __or_<_Bn...>::value;
172  template<typename... _Bn>
173  inline constexpr bool __and_v = __and_<_Bn...>::value;
174  /// @endcond
175 
176 #define __cpp_lib_logical_traits 201510
177 
178  template<typename... _Bn>
179  struct conjunction
180  : __and_<_Bn...>
181  { };
182 
183  template<typename... _Bn>
184  struct disjunction
185  : __or_<_Bn...>
186  { };
187 
188  template<typename _Pp>
189  struct negation
190  : __not_<_Pp>
191  { };
192 
193  /** @ingroup variable_templates
194  * @{
195  */
196  template<typename... _Bn>
197  inline constexpr bool conjunction_v = conjunction<_Bn...>::value;
198 
199  template<typename... _Bn>
200  inline constexpr bool disjunction_v = disjunction<_Bn...>::value;
201 
202  template<typename _Pp>
203  inline constexpr bool negation_v = negation<_Pp>::value;
204  /// @}
205 
206 #endif // C++17
207 
208  // Forward declarations
209  template<typename>
210  struct is_reference;
211  template<typename>
212  struct is_function;
213  template<typename>
214  struct is_void;
215  template<typename>
216  struct remove_cv;
217  template<typename>
218  struct is_const;
219 
220  /// @cond undocumented
221  template<typename>
222  struct __is_array_unknown_bounds;
223 
224  // Helper functions that return false_type for incomplete classes,
225  // incomplete unions and arrays of known bound from those.
226 
227  template <typename _Tp, size_t = sizeof(_Tp)>
228  constexpr true_type __is_complete_or_unbounded(__type_identity<_Tp>)
229  { return {}; }
230 
231  template <typename _TypeIdentity,
232  typename _NestedType = typename _TypeIdentity::type>
233  constexpr typename __or_<
234  is_reference<_NestedType>,
235  is_function<_NestedType>,
236  is_void<_NestedType>,
237  __is_array_unknown_bounds<_NestedType>
238  >::type __is_complete_or_unbounded(_TypeIdentity)
239  { return {}; }
240 
241  // For several sfinae-friendly trait implementations we transport both the
242  // result information (as the member type) and the failure information (no
243  // member type). This is very similar to std::enable_if, but we cannot use
244  // them, because we need to derive from them as an implementation detail.
245 
246  template<typename _Tp>
247  struct __success_type
248  { typedef _Tp type; };
249 
250  struct __failure_type
251  { };
252 
253  // __remove_cv_t (std::remove_cv_t for C++11).
254  template<typename _Tp>
255  using __remove_cv_t = typename remove_cv<_Tp>::type;
256 
257  // Primary type categories.
258 
259  template<typename>
260  struct __is_void_helper
261  : public false_type { };
262 
263  template<>
264  struct __is_void_helper<void>
265  : public true_type { };
266  /// @endcond
267 
268  /// is_void
269  template<typename _Tp>
270  struct is_void
271  : public __is_void_helper<__remove_cv_t<_Tp>>::type
272  { };
273 
274  /// @cond undocumented
275  template<typename>
276  struct __is_integral_helper
277  : public false_type { };
278 
279  template<>
280  struct __is_integral_helper<bool>
281  : public true_type { };
282 
283  template<>
284  struct __is_integral_helper<char>
285  : public true_type { };
286 
287  template<>
288  struct __is_integral_helper<signed char>
289  : public true_type { };
290 
291  template<>
292  struct __is_integral_helper<unsigned char>
293  : public true_type { };
294 
295  // We want is_integral<wchar_t> to be true (and make_signed/unsigned to work)
296  // even when libc doesn't provide working <wchar.h> and related functions,
297  // so check __WCHAR_TYPE__ instead of _GLIBCXX_USE_WCHAR_T.
298 #ifdef __WCHAR_TYPE__
299  template<>
300  struct __is_integral_helper<wchar_t>
301  : public true_type { };
302 #endif
303 
304 #ifdef _GLIBCXX_USE_CHAR8_T
305  template<>
306  struct __is_integral_helper<char8_t>
307  : public true_type { };
308 #endif
309 
310  template<>
311  struct __is_integral_helper<char16_t>
312  : public true_type { };
313 
314  template<>
315  struct __is_integral_helper<char32_t>
316  : public true_type { };
317 
318  template<>
319  struct __is_integral_helper<short>
320  : public true_type { };
321 
322  template<>
323  struct __is_integral_helper<unsigned short>
324  : public true_type { };
325 
326  template<>
327  struct __is_integral_helper<int>
328  : public true_type { };
329 
330  template<>
331  struct __is_integral_helper<unsigned int>
332  : public true_type { };
333 
334  template<>
335  struct __is_integral_helper<long>
336  : public true_type { };
337 
338  template<>
339  struct __is_integral_helper<unsigned long>
340  : public true_type { };
341 
342  template<>
343  struct __is_integral_helper<long long>
344  : public true_type { };
345 
346  template<>
347  struct __is_integral_helper<unsigned long long>
348  : public true_type { };
349 
350  // Conditionalizing on __STRICT_ANSI__ here will break any port that
351  // uses one of these types for size_t.
352 #if defined(__GLIBCXX_TYPE_INT_N_0)
353  template<>
354  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_0>
355  : public true_type { };
356 
357  template<>
358  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_0>
359  : public true_type { };
360 #endif
361 #if defined(__GLIBCXX_TYPE_INT_N_1)
362  template<>
363  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_1>
364  : public true_type { };
365 
366  template<>
367  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_1>
368  : public true_type { };
369 #endif
370 #if defined(__GLIBCXX_TYPE_INT_N_2)
371  template<>
372  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_2>
373  : public true_type { };
374 
375  template<>
376  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_2>
377  : public true_type { };
378 #endif
379 #if defined(__GLIBCXX_TYPE_INT_N_3)
380  template<>
381  struct __is_integral_helper<__GLIBCXX_TYPE_INT_N_3>
382  : public true_type { };
383 
384  template<>
385  struct __is_integral_helper<unsigned __GLIBCXX_TYPE_INT_N_3>
386  : public true_type { };
387 #endif
388  /// @endcond
389 
390  /// is_integral
391  template<typename _Tp>
392  struct is_integral
393  : public __is_integral_helper<__remove_cv_t<_Tp>>::type
394  { };
395 
396  /// @cond undocumented
397  template<typename>
398  struct __is_floating_point_helper
399  : public false_type { };
400 
401  template<>
402  struct __is_floating_point_helper<float>
403  : public true_type { };
404 
405  template<>
406  struct __is_floating_point_helper<double>
407  : public true_type { };
408 
409  template<>
410  struct __is_floating_point_helper<long double>
411  : public true_type { };
412 
413 #if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128)
414  template<>
415  struct __is_floating_point_helper<__float128>
416  : public true_type { };
417 #endif
418  /// @endcond
419 
420  /// is_floating_point
421  template<typename _Tp>
423  : public __is_floating_point_helper<__remove_cv_t<_Tp>>::type
424  { };
425 
426  /// is_array
427  template<typename>
428  struct is_array
429  : public false_type { };
430 
431  template<typename _Tp, std::size_t _Size>
432  struct is_array<_Tp[_Size]>
433  : public true_type { };
434 
435  template<typename _Tp>
436  struct is_array<_Tp[]>
437  : public true_type { };
438 
439  template<typename>
440  struct __is_pointer_helper
441  : public false_type { };
442 
443  template<typename _Tp>
444  struct __is_pointer_helper<_Tp*>
445  : public true_type { };
446 
447  /// is_pointer
448  template<typename _Tp>
449  struct is_pointer
450  : public __is_pointer_helper<__remove_cv_t<_Tp>>::type
451  { };
452 
453  /// is_lvalue_reference
454  template<typename>
456  : public false_type { };
457 
458  template<typename _Tp>
459  struct is_lvalue_reference<_Tp&>
460  : public true_type { };
461 
462  /// is_rvalue_reference
463  template<typename>
465  : public false_type { };
466 
467  template<typename _Tp>
468  struct is_rvalue_reference<_Tp&&>
469  : public true_type { };
470 
471  template<typename>
472  struct __is_member_object_pointer_helper
473  : public false_type { };
474 
475  template<typename _Tp, typename _Cp>
476  struct __is_member_object_pointer_helper<_Tp _Cp::*>
477  : public __not_<is_function<_Tp>>::type { };
478 
479  /// is_member_object_pointer
480  template<typename _Tp>
482  : public __is_member_object_pointer_helper<__remove_cv_t<_Tp>>::type
483  { };
484 
485  template<typename>
486  struct __is_member_function_pointer_helper
487  : public false_type { };
488 
489  template<typename _Tp, typename _Cp>
490  struct __is_member_function_pointer_helper<_Tp _Cp::*>
491  : public is_function<_Tp>::type { };
492 
493  /// is_member_function_pointer
494  template<typename _Tp>
496  : public __is_member_function_pointer_helper<__remove_cv_t<_Tp>>::type
497  { };
498 
499  /// is_enum
500  template<typename _Tp>
501  struct is_enum
502  : public integral_constant<bool, __is_enum(_Tp)>
503  { };
504 
505  /// is_union
506  template<typename _Tp>
507  struct is_union
508  : public integral_constant<bool, __is_union(_Tp)>
509  { };
510 
511  /// is_class
512  template<typename _Tp>
513  struct is_class
514  : public integral_constant<bool, __is_class(_Tp)>
515  { };
516 
517  /// is_function
518  template<typename _Tp>
519  struct is_function
520  : public __bool_constant<!is_const<const _Tp>::value> { };
521 
522  template<typename _Tp>
523  struct is_function<_Tp&>
524  : public false_type { };
525 
526  template<typename _Tp>
527  struct is_function<_Tp&&>
528  : public false_type { };
529 
530 #define __cpp_lib_is_null_pointer 201309
531 
532  template<typename>
533  struct __is_null_pointer_helper
534  : public false_type { };
535 
536  template<>
537  struct __is_null_pointer_helper<std::nullptr_t>
538  : public true_type { };
539 
540  /// is_null_pointer (LWG 2247).
541  template<typename _Tp>
543  : public __is_null_pointer_helper<__remove_cv_t<_Tp>>::type
544  { };
545 
546  /// __is_nullptr_t (deprecated extension).
547  /// @deprecated Use `is_null_pointer` instead.
548  template<typename _Tp>
550  : public is_null_pointer<_Tp>
551  { } _GLIBCXX_DEPRECATED_SUGGEST("std::is_null_pointer");
552 
553  // Composite type categories.
554 
555  /// is_reference
556  template<typename _Tp>
558  : public __or_<is_lvalue_reference<_Tp>,
559  is_rvalue_reference<_Tp>>::type
560  { };
561 
562  /// is_arithmetic
563  template<typename _Tp>
565  : public __or_<is_integral<_Tp>, is_floating_point<_Tp>>::type
566  { };
567 
568  /// is_fundamental
569  template<typename _Tp>
571  : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
572  is_null_pointer<_Tp>>::type
573  { };
574 
575  /// is_object
576  template<typename _Tp>
577  struct is_object
578  : public __not_<__or_<is_function<_Tp>, is_reference<_Tp>,
579  is_void<_Tp>>>::type
580  { };
581 
582  template<typename>
583  struct is_member_pointer;
584 
585  /// is_scalar
586  template<typename _Tp>
587  struct is_scalar
588  : public __or_<is_arithmetic<_Tp>, is_enum<_Tp>, is_pointer<_Tp>,
589  is_member_pointer<_Tp>, is_null_pointer<_Tp>>::type
590  { };
591 
592  /// is_compound
593  template<typename _Tp>
594  struct is_compound
595  : public __not_<is_fundamental<_Tp>>::type { };
596 
597  /// @cond undocumented
598  template<typename _Tp>
599  struct __is_member_pointer_helper
600  : public false_type { };
601 
602  template<typename _Tp, typename _Cp>
603  struct __is_member_pointer_helper<_Tp _Cp::*>
604  : public true_type { };
605  /// @endcond
606 
607  /// is_member_pointer
608  template<typename _Tp>
610  : public __is_member_pointer_helper<__remove_cv_t<_Tp>>::type
611  { };
612 
613  template<typename, typename>
614  struct is_same;
615 
616  /// @cond undocumented
617  template<typename _Tp, typename... _Types>
618  using __is_one_of = __or_<is_same<_Tp, _Types>...>;
619 
620  // Check if a type is one of the signed integer types.
621  template<typename _Tp>
622  using __is_signed_integer = __is_one_of<__remove_cv_t<_Tp>,
623  signed char, signed short, signed int, signed long,
624  signed long long
625 #if defined(__GLIBCXX_TYPE_INT_N_0)
626  , signed __GLIBCXX_TYPE_INT_N_0
627 #endif
628 #if defined(__GLIBCXX_TYPE_INT_N_1)
629  , signed __GLIBCXX_TYPE_INT_N_1
630 #endif
631 #if defined(__GLIBCXX_TYPE_INT_N_2)
632  , signed __GLIBCXX_TYPE_INT_N_2
633 #endif
634 #if defined(__GLIBCXX_TYPE_INT_N_3)
635  , signed __GLIBCXX_TYPE_INT_N_3
636 #endif
637  >;
638 
639  // Check if a type is one of the unsigned integer types.
640  template<typename _Tp>
641  using __is_unsigned_integer = __is_one_of<__remove_cv_t<_Tp>,
642  unsigned char, unsigned short, unsigned int, unsigned long,
643  unsigned long long
644 #if defined(__GLIBCXX_TYPE_INT_N_0)
645  , unsigned __GLIBCXX_TYPE_INT_N_0
646 #endif
647 #if defined(__GLIBCXX_TYPE_INT_N_1)
648  , unsigned __GLIBCXX_TYPE_INT_N_1
649 #endif
650 #if defined(__GLIBCXX_TYPE_INT_N_2)
651  , unsigned __GLIBCXX_TYPE_INT_N_2
652 #endif
653 #if defined(__GLIBCXX_TYPE_INT_N_3)
654  , unsigned __GLIBCXX_TYPE_INT_N_3
655 #endif
656  >;
657 
658  // Check if a type is one of the signed or unsigned integer types.
659  template<typename _Tp>
660  using __is_standard_integer
661  = __or_<__is_signed_integer<_Tp>, __is_unsigned_integer<_Tp>>;
662 
663  // __void_t (std::void_t for C++11)
664  template<typename...> using __void_t = void;
665 
666  // Utility to detect referenceable types ([defns.referenceable]).
667 
668  template<typename _Tp, typename = void>
669  struct __is_referenceable
670  : public false_type
671  { };
672 
673  template<typename _Tp>
674  struct __is_referenceable<_Tp, __void_t<_Tp&>>
675  : public true_type
676  { };
677  /// @endcond
678 
679  // Type properties.
680 
681  /// is_const
682  template<typename>
683  struct is_const
684  : public false_type { };
685 
686  template<typename _Tp>
687  struct is_const<_Tp const>
688  : public true_type { };
689 
690  /// is_volatile
691  template<typename>
692  struct is_volatile
693  : public false_type { };
694 
695  template<typename _Tp>
696  struct is_volatile<_Tp volatile>
697  : public true_type { };
698 
699  /// is_trivial
700  template<typename _Tp>
701  struct is_trivial
702  : public integral_constant<bool, __is_trivial(_Tp)>
703  {
704  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
705  "template argument must be a complete class or an unbounded array");
706  };
707 
708  /// is_trivially_copyable
709  template<typename _Tp>
711  : public integral_constant<bool, __is_trivially_copyable(_Tp)>
712  {
713  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
714  "template argument must be a complete class or an unbounded array");
715  };
716 
717  /// is_standard_layout
718  template<typename _Tp>
720  : public integral_constant<bool, __is_standard_layout(_Tp)>
721  {
722  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
723  "template argument must be a complete class or an unbounded array");
724  };
725 
726  /** is_pod (deprecated in C++20)
727  * @deprecated Use `is_standard_layout && is_trivial` instead.
728  */
729  // Could use is_standard_layout && is_trivial instead of the builtin.
730  template<typename _Tp>
731  struct
732  _GLIBCXX20_DEPRECATED("use is_standard_layout && is_trivial instead")
733  is_pod
734  : public integral_constant<bool, __is_pod(_Tp)>
735  {
736  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
737  "template argument must be a complete class or an unbounded array");
738  };
739 
740  /** is_literal_type
741  * @deprecated Deprecated in C++20. The idea of a literal type isn't useful.
742  */
743  template<typename _Tp>
744  struct
745  _GLIBCXX17_DEPRECATED
747  : public integral_constant<bool, __is_literal_type(_Tp)>
748  {
749  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
750  "template argument must be a complete class or an unbounded array");
751  };
752 
753  /// is_empty
754  template<typename _Tp>
755  struct is_empty
756  : public integral_constant<bool, __is_empty(_Tp)>
757  { };
758 
759  /// is_polymorphic
760  template<typename _Tp>
762  : public integral_constant<bool, __is_polymorphic(_Tp)>
763  { };
764 
765 #if __cplusplus >= 201402L
766 #define __cpp_lib_is_final 201402L
767  /// is_final
768  /// @since C++14
769  template<typename _Tp>
770  struct is_final
771  : public integral_constant<bool, __is_final(_Tp)>
772  { };
773 #endif
774 
775  /// is_abstract
776  template<typename _Tp>
777  struct is_abstract
778  : public integral_constant<bool, __is_abstract(_Tp)>
779  { };
780 
781  /// @cond undocumented
782  template<typename _Tp,
784  struct __is_signed_helper
785  : public false_type { };
786 
787  template<typename _Tp>
788  struct __is_signed_helper<_Tp, true>
789  : public integral_constant<bool, _Tp(-1) < _Tp(0)>
790  { };
791  /// @endcond
792 
793  /// is_signed
794  template<typename _Tp>
795  struct is_signed
796  : public __is_signed_helper<_Tp>::type
797  { };
798 
799  /// is_unsigned
800  template<typename _Tp>
801  struct is_unsigned
802  : public __and_<is_arithmetic<_Tp>, __not_<is_signed<_Tp>>>
803  { };
804 
805  /// @cond undocumented
806  template<typename _Tp, typename _Up = _Tp&&>
807  _Up
808  __declval(int);
809 
810  template<typename _Tp>
811  _Tp
812  __declval(long);
813  /// @endcond
814 
815  template<typename _Tp>
816  auto declval() noexcept -> decltype(__declval<_Tp>(0));
817 
818  template<typename, unsigned = 0>
819  struct extent;
820 
821  template<typename>
822  struct remove_all_extents;
823 
824  /// @cond undocumented
825  template<typename _Tp>
826  struct __is_array_known_bounds
827  : public integral_constant<bool, (extent<_Tp>::value > 0)>
828  { };
829 
830  template<typename _Tp>
831  struct __is_array_unknown_bounds
832  : public __and_<is_array<_Tp>, __not_<extent<_Tp>>>
833  { };
834 
835  // Destructible and constructible type properties.
836 
837  // In N3290 is_destructible does not say anything about function
838  // types and abstract types, see LWG 2049. This implementation
839  // describes function types as non-destructible and all complete
840  // object types as destructible, iff the explicit destructor
841  // call expression is wellformed.
842  struct __do_is_destructible_impl
843  {
844  template<typename _Tp, typename = decltype(declval<_Tp&>().~_Tp())>
845  static true_type __test(int);
846 
847  template<typename>
848  static false_type __test(...);
849  };
850 
851  template<typename _Tp>
852  struct __is_destructible_impl
853  : public __do_is_destructible_impl
854  {
855  typedef decltype(__test<_Tp>(0)) type;
856  };
857 
858  template<typename _Tp,
859  bool = __or_<is_void<_Tp>,
860  __is_array_unknown_bounds<_Tp>,
861  is_function<_Tp>>::value,
862  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
863  struct __is_destructible_safe;
864 
865  template<typename _Tp>
866  struct __is_destructible_safe<_Tp, false, false>
867  : public __is_destructible_impl<typename
868  remove_all_extents<_Tp>::type>::type
869  { };
870 
871  template<typename _Tp>
872  struct __is_destructible_safe<_Tp, true, false>
873  : public false_type { };
874 
875  template<typename _Tp>
876  struct __is_destructible_safe<_Tp, false, true>
877  : public true_type { };
878  /// @endcond
879 
880  /// is_destructible
881  template<typename _Tp>
883  : public __is_destructible_safe<_Tp>::type
884  {
885  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
886  "template argument must be a complete class or an unbounded array");
887  };
888 
889  /// @cond undocumented
890 
891  // is_nothrow_destructible requires that is_destructible is
892  // satisfied as well. We realize that by mimicing the
893  // implementation of is_destructible but refer to noexcept(expr)
894  // instead of decltype(expr).
895  struct __do_is_nt_destructible_impl
896  {
897  template<typename _Tp>
898  static __bool_constant<noexcept(declval<_Tp&>().~_Tp())>
899  __test(int);
900 
901  template<typename>
902  static false_type __test(...);
903  };
904 
905  template<typename _Tp>
906  struct __is_nt_destructible_impl
907  : public __do_is_nt_destructible_impl
908  {
909  typedef decltype(__test<_Tp>(0)) type;
910  };
911 
912  template<typename _Tp,
913  bool = __or_<is_void<_Tp>,
914  __is_array_unknown_bounds<_Tp>,
915  is_function<_Tp>>::value,
916  bool = __or_<is_reference<_Tp>, is_scalar<_Tp>>::value>
917  struct __is_nt_destructible_safe;
918 
919  template<typename _Tp>
920  struct __is_nt_destructible_safe<_Tp, false, false>
921  : public __is_nt_destructible_impl<typename
922  remove_all_extents<_Tp>::type>::type
923  { };
924 
925  template<typename _Tp>
926  struct __is_nt_destructible_safe<_Tp, true, false>
927  : public false_type { };
928 
929  template<typename _Tp>
930  struct __is_nt_destructible_safe<_Tp, false, true>
931  : public true_type { };
932  /// @endcond
933 
934  /// is_nothrow_destructible
935  template<typename _Tp>
937  : public __is_nt_destructible_safe<_Tp>::type
938  {
939  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
940  "template argument must be a complete class or an unbounded array");
941  };
942 
943  /// @cond undocumented
944  template<typename _Tp, typename... _Args>
945  struct __is_constructible_impl
946  : public __bool_constant<__is_constructible(_Tp, _Args...)>
947  { };
948  /// @endcond
949 
950  /// is_constructible
951  template<typename _Tp, typename... _Args>
953  : public __is_constructible_impl<_Tp, _Args...>
954  {
955  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
956  "template argument must be a complete class or an unbounded array");
957  };
958 
959  /// is_default_constructible
960  template<typename _Tp>
962  : public __is_constructible_impl<_Tp>::type
963  {
964  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
965  "template argument must be a complete class or an unbounded array");
966  };
967 
968  /// @cond undocumented
969  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
970  struct __is_copy_constructible_impl;
971 
972  template<typename _Tp>
973  struct __is_copy_constructible_impl<_Tp, false>
974  : public false_type { };
975 
976  template<typename _Tp>
977  struct __is_copy_constructible_impl<_Tp, true>
978  : public __is_constructible_impl<_Tp, const _Tp&>
979  { };
980  /// @endcond
981 
982  /// is_copy_constructible
983  template<typename _Tp>
985  : public __is_copy_constructible_impl<_Tp>
986  {
987  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
988  "template argument must be a complete class or an unbounded array");
989  };
990 
991  /// @cond undocumented
992  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
993  struct __is_move_constructible_impl;
994 
995  template<typename _Tp>
996  struct __is_move_constructible_impl<_Tp, false>
997  : public false_type { };
998 
999  template<typename _Tp>
1000  struct __is_move_constructible_impl<_Tp, true>
1001  : public __is_constructible_impl<_Tp, _Tp&&>
1002  { };
1003  /// @endcond
1004 
1005  /// is_move_constructible
1006  template<typename _Tp>
1008  : public __is_move_constructible_impl<_Tp>
1009  {
1010  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1011  "template argument must be a complete class or an unbounded array");
1012  };
1013 
1014  /// @cond undocumented
1015  template<typename _Tp, typename... _Args>
1016  using __is_nothrow_constructible_impl
1017  = __bool_constant<__is_nothrow_constructible(_Tp, _Args...)>;
1018  /// @endcond
1019 
1020  /// is_nothrow_constructible
1021  template<typename _Tp, typename... _Args>
1023  : public __is_nothrow_constructible_impl<_Tp, _Args...>::type
1024  {
1025  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1026  "template argument must be a complete class or an unbounded array");
1027  };
1028 
1029  /// is_nothrow_default_constructible
1030  template<typename _Tp>
1032  : public __bool_constant<__is_nothrow_constructible(_Tp)>
1033  {
1034  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1035  "template argument must be a complete class or an unbounded array");
1036  };
1037 
1038  /// @cond undocumented
1039  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1040  struct __is_nothrow_copy_constructible_impl;
1041 
1042  template<typename _Tp>
1043  struct __is_nothrow_copy_constructible_impl<_Tp, false>
1044  : public false_type { };
1045 
1046  template<typename _Tp>
1047  struct __is_nothrow_copy_constructible_impl<_Tp, true>
1048  : public __is_nothrow_constructible_impl<_Tp, const _Tp&>
1049  { };
1050  /// @endcond
1051 
1052  /// is_nothrow_copy_constructible
1053  template<typename _Tp>
1055  : public __is_nothrow_copy_constructible_impl<_Tp>::type
1056  {
1057  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1058  "template argument must be a complete class or an unbounded array");
1059  };
1060 
1061  /// @cond undocumented
1062  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1063  struct __is_nothrow_move_constructible_impl;
1064 
1065  template<typename _Tp>
1066  struct __is_nothrow_move_constructible_impl<_Tp, false>
1067  : public false_type { };
1068 
1069  template<typename _Tp>
1070  struct __is_nothrow_move_constructible_impl<_Tp, true>
1071  : public __is_nothrow_constructible_impl<_Tp, _Tp&&>
1072  { };
1073  /// @endcond
1074 
1075  /// is_nothrow_move_constructible
1076  template<typename _Tp>
1078  : public __is_nothrow_move_constructible_impl<_Tp>::type
1079  {
1080  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1081  "template argument must be a complete class or an unbounded array");
1082  };
1083 
1084  /// is_assignable
1085  template<typename _Tp, typename _Up>
1087  : public __bool_constant<__is_assignable(_Tp, _Up)>
1088  {
1089  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1090  "template argument must be a complete class or an unbounded array");
1091  };
1092 
1093  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1094  struct __is_copy_assignable_impl;
1095 
1096  template<typename _Tp>
1097  struct __is_copy_assignable_impl<_Tp, false>
1098  : public false_type { };
1099 
1100  template<typename _Tp>
1101  struct __is_copy_assignable_impl<_Tp, true>
1102  : public __bool_constant<__is_assignable(_Tp&, const _Tp&)>
1103  { };
1104 
1105  /// is_copy_assignable
1106  template<typename _Tp>
1108  : public __is_copy_assignable_impl<_Tp>::type
1109  {
1110  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1111  "template argument must be a complete class or an unbounded array");
1112  };
1113 
1114  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1115  struct __is_move_assignable_impl;
1116 
1117  template<typename _Tp>
1118  struct __is_move_assignable_impl<_Tp, false>
1119  : public false_type { };
1120 
1121  template<typename _Tp>
1122  struct __is_move_assignable_impl<_Tp, true>
1123  : public __bool_constant<__is_assignable(_Tp&, _Tp&&)>
1124  { };
1125 
1126  /// is_move_assignable
1127  template<typename _Tp>
1129  : public __is_move_assignable_impl<_Tp>::type
1130  {
1131  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1132  "template argument must be a complete class or an unbounded array");
1133  };
1134 
1135  template<typename _Tp, typename _Up>
1136  using __is_nothrow_assignable_impl
1137  = __bool_constant<__is_nothrow_assignable(_Tp, _Up)>;
1138 
1139  /// is_nothrow_assignable
1140  template<typename _Tp, typename _Up>
1142  : public __is_nothrow_assignable_impl<_Tp, _Up>
1143  {
1144  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1145  "template argument must be a complete class or an unbounded array");
1146  };
1147 
1148  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1149  struct __is_nt_copy_assignable_impl;
1150 
1151  template<typename _Tp>
1152  struct __is_nt_copy_assignable_impl<_Tp, false>
1153  : public false_type { };
1154 
1155  template<typename _Tp>
1156  struct __is_nt_copy_assignable_impl<_Tp, true>
1157  : public __is_nothrow_assignable_impl<_Tp&, const _Tp&>
1158  { };
1159 
1160  /// is_nothrow_copy_assignable
1161  template<typename _Tp>
1163  : public __is_nt_copy_assignable_impl<_Tp>
1164  {
1165  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1166  "template argument must be a complete class or an unbounded array");
1167  };
1168 
1169  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1170  struct __is_nt_move_assignable_impl;
1171 
1172  template<typename _Tp>
1173  struct __is_nt_move_assignable_impl<_Tp, false>
1174  : public false_type { };
1175 
1176  template<typename _Tp>
1177  struct __is_nt_move_assignable_impl<_Tp, true>
1178  : public __is_nothrow_assignable_impl<_Tp&, _Tp&&>
1179  { };
1180 
1181  /// is_nothrow_move_assignable
1182  template<typename _Tp>
1184  : public __is_nt_move_assignable_impl<_Tp>
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_trivially_constructible
1191  template<typename _Tp, typename... _Args>
1193  : public __bool_constant<__is_trivially_constructible(_Tp, _Args...)>
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_trivially_default_constructible
1200  template<typename _Tp>
1202  : public __bool_constant<__is_trivially_constructible(_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  struct __do_is_implicitly_default_constructible_impl
1209  {
1210  template <typename _Tp>
1211  static void __helper(const _Tp&);
1212 
1213  template <typename _Tp>
1214  static true_type __test(const _Tp&,
1215  decltype(__helper<const _Tp&>({}))* = 0);
1216 
1217  static false_type __test(...);
1218  };
1219 
1220  template<typename _Tp>
1221  struct __is_implicitly_default_constructible_impl
1222  : public __do_is_implicitly_default_constructible_impl
1223  {
1224  typedef decltype(__test(declval<_Tp>())) type;
1225  };
1226 
1227  template<typename _Tp>
1228  struct __is_implicitly_default_constructible_safe
1229  : public __is_implicitly_default_constructible_impl<_Tp>::type
1230  { };
1231 
1232  template <typename _Tp>
1233  struct __is_implicitly_default_constructible
1234  : public __and_<__is_constructible_impl<_Tp>,
1235  __is_implicitly_default_constructible_safe<_Tp>>
1236  { };
1237 
1238  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1239  struct __is_trivially_copy_constructible_impl;
1240 
1241  template<typename _Tp>
1242  struct __is_trivially_copy_constructible_impl<_Tp, false>
1243  : public false_type { };
1244 
1245  template<typename _Tp>
1246  struct __is_trivially_copy_constructible_impl<_Tp, true>
1247  : public __and_<__is_copy_constructible_impl<_Tp>,
1248  integral_constant<bool,
1249  __is_trivially_constructible(_Tp, const _Tp&)>>
1250  { };
1251 
1252  /// is_trivially_copy_constructible
1253  template<typename _Tp>
1255  : public __is_trivially_copy_constructible_impl<_Tp>
1256  {
1257  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1258  "template argument must be a complete class or an unbounded array");
1259  };
1260 
1261  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1262  struct __is_trivially_move_constructible_impl;
1263 
1264  template<typename _Tp>
1265  struct __is_trivially_move_constructible_impl<_Tp, false>
1266  : public false_type { };
1267 
1268  template<typename _Tp>
1269  struct __is_trivially_move_constructible_impl<_Tp, true>
1270  : public __and_<__is_move_constructible_impl<_Tp>,
1271  integral_constant<bool,
1272  __is_trivially_constructible(_Tp, _Tp&&)>>
1273  { };
1274 
1275  /// is_trivially_move_constructible
1276  template<typename _Tp>
1278  : public __is_trivially_move_constructible_impl<_Tp>
1279  {
1280  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1281  "template argument must be a complete class or an unbounded array");
1282  };
1283 
1284  /// is_trivially_assignable
1285  template<typename _Tp, typename _Up>
1287  : public __bool_constant<__is_trivially_assignable(_Tp, _Up)>
1288  {
1289  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1290  "template argument must be a complete class or an unbounded array");
1291  };
1292 
1293  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1294  struct __is_trivially_copy_assignable_impl;
1295 
1296  template<typename _Tp>
1297  struct __is_trivially_copy_assignable_impl<_Tp, false>
1298  : public false_type { };
1299 
1300  template<typename _Tp>
1301  struct __is_trivially_copy_assignable_impl<_Tp, true>
1302  : public __bool_constant<__is_trivially_assignable(_Tp&, const _Tp&)>
1303  { };
1304 
1305  /// is_trivially_copy_assignable
1306  template<typename _Tp>
1308  : public __is_trivially_copy_assignable_impl<_Tp>
1309  {
1310  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1311  "template argument must be a complete class or an unbounded array");
1312  };
1313 
1314  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1315  struct __is_trivially_move_assignable_impl;
1316 
1317  template<typename _Tp>
1318  struct __is_trivially_move_assignable_impl<_Tp, false>
1319  : public false_type { };
1320 
1321  template<typename _Tp>
1322  struct __is_trivially_move_assignable_impl<_Tp, true>
1323  : public __bool_constant<__is_trivially_assignable(_Tp&, _Tp&&)>
1324  { };
1325 
1326  /// is_trivially_move_assignable
1327  template<typename _Tp>
1329  : public __is_trivially_move_assignable_impl<_Tp>
1330  {
1331  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1332  "template argument must be a complete class or an unbounded array");
1333  };
1334 
1335  /// is_trivially_destructible
1336  template<typename _Tp>
1338  : public __and_<__is_destructible_safe<_Tp>,
1339  __bool_constant<__has_trivial_destructor(_Tp)>>
1340  {
1341  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1342  "template argument must be a complete class or an unbounded array");
1343  };
1344 
1345 
1346  /// has_virtual_destructor
1347  template<typename _Tp>
1349  : public integral_constant<bool, __has_virtual_destructor(_Tp)>
1350  {
1351  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1352  "template argument must be a complete class or an unbounded array");
1353  };
1354 
1355 
1356  // type property queries.
1357 
1358  /// alignment_of
1359  template<typename _Tp>
1361  : public integral_constant<std::size_t, alignof(_Tp)>
1362  {
1363  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
1364  "template argument must be a complete class or an unbounded array");
1365  };
1366 
1367  /// rank
1368  template<typename>
1369  struct rank
1370  : public integral_constant<std::size_t, 0> { };
1371 
1372  template<typename _Tp, std::size_t _Size>
1373  struct rank<_Tp[_Size]>
1374  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1375 
1376  template<typename _Tp>
1377  struct rank<_Tp[]>
1378  : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
1379 
1380  /// extent
1381  template<typename, unsigned _Uint>
1382  struct extent
1383  : public integral_constant<std::size_t, 0> { };
1384 
1385  template<typename _Tp, unsigned _Uint, std::size_t _Size>
1386  struct extent<_Tp[_Size], _Uint>
1387  : public integral_constant<std::size_t,
1388  _Uint == 0 ? _Size : extent<_Tp,
1389  _Uint - 1>::value>
1390  { };
1391 
1392  template<typename _Tp, unsigned _Uint>
1393  struct extent<_Tp[], _Uint>
1394  : public integral_constant<std::size_t,
1395  _Uint == 0 ? 0 : extent<_Tp,
1396  _Uint - 1>::value>
1397  { };
1398 
1399 
1400  // Type relations.
1401 
1402  /// is_same
1403  template<typename _Tp, typename _Up>
1404  struct is_same
1405 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
1406  : public integral_constant<bool, __is_same(_Tp, _Up)>
1407 #else
1408  : public false_type
1409 #endif
1410  { };
1411 
1412 #ifndef _GLIBCXX_HAVE_BUILTIN_IS_SAME
1413  template<typename _Tp>
1414  struct is_same<_Tp, _Tp>
1415  : public true_type
1416  { };
1417 #endif
1418 
1419  /// is_base_of
1420  template<typename _Base, typename _Derived>
1421  struct is_base_of
1422  : public integral_constant<bool, __is_base_of(_Base, _Derived)>
1423  { };
1424 
1425  template<typename _From, typename _To,
1426  bool = __or_<is_void<_From>, is_function<_To>,
1427  is_array<_To>>::value>
1428  struct __is_convertible_helper
1429  {
1430  typedef typename is_void<_To>::type type;
1431  };
1432 
1433 #pragma GCC diagnostic push
1434 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1435  template<typename _From, typename _To>
1436  class __is_convertible_helper<_From, _To, false>
1437  {
1438  template<typename _To1>
1439  static void __test_aux(_To1) noexcept;
1440 
1441  template<typename _From1, typename _To1,
1442  typename = decltype(__test_aux<_To1>(std::declval<_From1>()))>
1443  static true_type
1444  __test(int);
1445 
1446  template<typename, typename>
1447  static false_type
1448  __test(...);
1449 
1450  public:
1451  typedef decltype(__test<_From, _To>(0)) type;
1452  };
1453 #pragma GCC diagnostic pop
1454 
1455  /// is_convertible
1456  template<typename _From, typename _To>
1458  : public __is_convertible_helper<_From, _To>::type
1459  { };
1460 
1461  // helper trait for unique_ptr<T[]>, shared_ptr<T[]>, and span<T, N>
1462  template<typename _ToElementType, typename _FromElementType>
1464  = is_convertible<_FromElementType(*)[], _ToElementType(*)[]>;
1465 
1466  template<typename _From, typename _To,
1467  bool = __or_<is_void<_From>, is_function<_To>,
1468  is_array<_To>>::value>
1469  struct __is_nt_convertible_helper
1470  : is_void<_To>
1471  { };
1472 
1473 #pragma GCC diagnostic push
1474 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
1475  template<typename _From, typename _To>
1476  class __is_nt_convertible_helper<_From, _To, false>
1477  {
1478  template<typename _To1>
1479  static void __test_aux(_To1) noexcept;
1480 
1481  template<typename _From1, typename _To1>
1482  static
1483  __bool_constant<noexcept(__test_aux<_To1>(std::declval<_From1>()))>
1484  __test(int);
1485 
1486  template<typename, typename>
1487  static false_type
1488  __test(...);
1489 
1490  public:
1491  using type = decltype(__test<_From, _To>(0));
1492  };
1493 #pragma GCC diagnostic pop
1494 
1495  // is_nothrow_convertible for C++11
1496  template<typename _From, typename _To>
1497  struct __is_nothrow_convertible
1498  : public __is_nt_convertible_helper<_From, _To>::type
1499  { };
1500 
1501 #if __cplusplus > 201703L
1502 #define __cpp_lib_is_nothrow_convertible 201806L
1503  /// is_nothrow_convertible
1504  template<typename _From, typename _To>
1505  struct is_nothrow_convertible
1506  : public __is_nt_convertible_helper<_From, _To>::type
1507  { };
1508 
1509  /// is_nothrow_convertible_v
1510  template<typename _From, typename _To>
1511  inline constexpr bool is_nothrow_convertible_v
1512  = is_nothrow_convertible<_From, _To>::value;
1513 #endif // C++2a
1514 
1515  // Const-volatile modifications.
1516 
1517  /// remove_const
1518  template<typename _Tp>
1520  { typedef _Tp type; };
1521 
1522  template<typename _Tp>
1523  struct remove_const<_Tp const>
1524  { typedef _Tp type; };
1525 
1526  /// remove_volatile
1527  template<typename _Tp>
1529  { typedef _Tp type; };
1530 
1531  template<typename _Tp>
1532  struct remove_volatile<_Tp volatile>
1533  { typedef _Tp type; };
1534 
1535  /// remove_cv
1536  template<typename _Tp>
1537  struct remove_cv
1538  { using type = _Tp; };
1539 
1540  template<typename _Tp>
1541  struct remove_cv<const _Tp>
1542  { using type = _Tp; };
1543 
1544  template<typename _Tp>
1545  struct remove_cv<volatile _Tp>
1546  { using type = _Tp; };
1547 
1548  template<typename _Tp>
1549  struct remove_cv<const volatile _Tp>
1550  { using type = _Tp; };
1551 
1552  /// add_const
1553  template<typename _Tp>
1554  struct add_const
1555  { typedef _Tp const type; };
1556 
1557  /// add_volatile
1558  template<typename _Tp>
1560  { typedef _Tp volatile type; };
1561 
1562  /// add_cv
1563  template<typename _Tp>
1564  struct add_cv
1565  {
1566  typedef typename
1568  };
1569 
1570 #if __cplusplus > 201103L
1571 
1572 #define __cpp_lib_transformation_trait_aliases 201304
1573 
1574  /// Alias template for remove_const
1575  template<typename _Tp>
1576  using remove_const_t = typename remove_const<_Tp>::type;
1577 
1578  /// Alias template for remove_volatile
1579  template<typename _Tp>
1580  using remove_volatile_t = typename remove_volatile<_Tp>::type;
1581 
1582  /// Alias template for remove_cv
1583  template<typename _Tp>
1584  using remove_cv_t = typename remove_cv<_Tp>::type;
1585 
1586  /// Alias template for add_const
1587  template<typename _Tp>
1588  using add_const_t = typename add_const<_Tp>::type;
1589 
1590  /// Alias template for add_volatile
1591  template<typename _Tp>
1592  using add_volatile_t = typename add_volatile<_Tp>::type;
1593 
1594  /// Alias template for add_cv
1595  template<typename _Tp>
1596  using add_cv_t = typename add_cv<_Tp>::type;
1597 #endif
1598 
1599  // Reference transformations.
1600 
1601  /// remove_reference
1602  template<typename _Tp>
1604  { typedef _Tp type; };
1605 
1606  template<typename _Tp>
1607  struct remove_reference<_Tp&>
1608  { typedef _Tp type; };
1609 
1610  template<typename _Tp>
1611  struct remove_reference<_Tp&&>
1612  { typedef _Tp type; };
1613 
1614  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1615  struct __add_lvalue_reference_helper
1616  { typedef _Tp type; };
1617 
1618  template<typename _Tp>
1619  struct __add_lvalue_reference_helper<_Tp, true>
1620  { typedef _Tp& type; };
1621 
1622  /// add_lvalue_reference
1623  template<typename _Tp>
1625  : public __add_lvalue_reference_helper<_Tp>
1626  { };
1627 
1628  template<typename _Tp, bool = __is_referenceable<_Tp>::value>
1629  struct __add_rvalue_reference_helper
1630  { typedef _Tp type; };
1631 
1632  template<typename _Tp>
1633  struct __add_rvalue_reference_helper<_Tp, true>
1634  { typedef _Tp&& type; };
1635 
1636  /// add_rvalue_reference
1637  template<typename _Tp>
1639  : public __add_rvalue_reference_helper<_Tp>
1640  { };
1641 
1642 #if __cplusplus > 201103L
1643  /// Alias template for remove_reference
1644  template<typename _Tp>
1645  using remove_reference_t = typename remove_reference<_Tp>::type;
1646 
1647  /// Alias template for add_lvalue_reference
1648  template<typename _Tp>
1649  using add_lvalue_reference_t = typename add_lvalue_reference<_Tp>::type;
1650 
1651  /// Alias template for add_rvalue_reference
1652  template<typename _Tp>
1653  using add_rvalue_reference_t = typename add_rvalue_reference<_Tp>::type;
1654 #endif
1655 
1656  // Sign modifications.
1657 
1658  /// @cond undocumented
1659 
1660  // Utility for constructing identically cv-qualified types.
1661  template<typename _Unqualified, bool _IsConst, bool _IsVol>
1662  struct __cv_selector;
1663 
1664  template<typename _Unqualified>
1665  struct __cv_selector<_Unqualified, false, false>
1666  { typedef _Unqualified __type; };
1667 
1668  template<typename _Unqualified>
1669  struct __cv_selector<_Unqualified, false, true>
1670  { typedef volatile _Unqualified __type; };
1671 
1672  template<typename _Unqualified>
1673  struct __cv_selector<_Unqualified, true, false>
1674  { typedef const _Unqualified __type; };
1675 
1676  template<typename _Unqualified>
1677  struct __cv_selector<_Unqualified, true, true>
1678  { typedef const volatile _Unqualified __type; };
1679 
1680  template<typename _Qualified, typename _Unqualified,
1681  bool _IsConst = is_const<_Qualified>::value,
1682  bool _IsVol = is_volatile<_Qualified>::value>
1683  class __match_cv_qualifiers
1684  {
1685  typedef __cv_selector<_Unqualified, _IsConst, _IsVol> __match;
1686 
1687  public:
1688  typedef typename __match::__type __type;
1689  };
1690 
1691  // Utility for finding the unsigned versions of signed integral types.
1692  template<typename _Tp>
1693  struct __make_unsigned
1694  { typedef _Tp __type; };
1695 
1696  template<>
1697  struct __make_unsigned<char>
1698  { typedef unsigned char __type; };
1699 
1700  template<>
1701  struct __make_unsigned<signed char>
1702  { typedef unsigned char __type; };
1703 
1704  template<>
1705  struct __make_unsigned<short>
1706  { typedef unsigned short __type; };
1707 
1708  template<>
1709  struct __make_unsigned<int>
1710  { typedef unsigned int __type; };
1711 
1712  template<>
1713  struct __make_unsigned<long>
1714  { typedef unsigned long __type; };
1715 
1716  template<>
1717  struct __make_unsigned<long long>
1718  { typedef unsigned long long __type; };
1719 
1720 #if defined(__GLIBCXX_TYPE_INT_N_0)
1721  template<>
1722  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_0>
1723  { typedef unsigned __GLIBCXX_TYPE_INT_N_0 __type; };
1724 #endif
1725 #if defined(__GLIBCXX_TYPE_INT_N_1)
1726  template<>
1727  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_1>
1728  { typedef unsigned __GLIBCXX_TYPE_INT_N_1 __type; };
1729 #endif
1730 #if defined(__GLIBCXX_TYPE_INT_N_2)
1731  template<>
1732  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_2>
1733  { typedef unsigned __GLIBCXX_TYPE_INT_N_2 __type; };
1734 #endif
1735 #if defined(__GLIBCXX_TYPE_INT_N_3)
1736  template<>
1737  struct __make_unsigned<__GLIBCXX_TYPE_INT_N_3>
1738  { typedef unsigned __GLIBCXX_TYPE_INT_N_3 __type; };
1739 #endif
1740 
1741  // Select between integral and enum: not possible to be both.
1742  template<typename _Tp,
1743  bool _IsInt = is_integral<_Tp>::value,
1744  bool _IsEnum = is_enum<_Tp>::value>
1745  class __make_unsigned_selector;
1746 
1747  template<typename _Tp>
1748  class __make_unsigned_selector<_Tp, true, false>
1749  {
1750  using __unsigned_type
1751  = typename __make_unsigned<__remove_cv_t<_Tp>>::__type;
1752 
1753  public:
1754  using __type
1755  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1756  };
1757 
1758  class __make_unsigned_selector_base
1759  {
1760  protected:
1761  template<typename...> struct _List { };
1762 
1763  template<typename _Tp, typename... _Up>
1764  struct _List<_Tp, _Up...> : _List<_Up...>
1765  { static constexpr size_t __size = sizeof(_Tp); };
1766 
1767  template<size_t _Sz, typename _Tp, bool = (_Sz <= _Tp::__size)>
1768  struct __select;
1769 
1770  template<size_t _Sz, typename _Uint, typename... _UInts>
1771  struct __select<_Sz, _List<_Uint, _UInts...>, true>
1772  { using __type = _Uint; };
1773 
1774  template<size_t _Sz, typename _Uint, typename... _UInts>
1775  struct __select<_Sz, _List<_Uint, _UInts...>, false>
1776  : __select<_Sz, _List<_UInts...>>
1777  { };
1778  };
1779 
1780  // Choose unsigned integer type with the smallest rank and same size as _Tp
1781  template<typename _Tp>
1782  class __make_unsigned_selector<_Tp, false, true>
1783  : __make_unsigned_selector_base
1784  {
1785  // With -fshort-enums, an enum may be as small as a char.
1786  using _UInts = _List<unsigned char, unsigned short, unsigned int,
1787  unsigned long, unsigned long long>;
1788 
1789  using __unsigned_type = typename __select<sizeof(_Tp), _UInts>::__type;
1790 
1791  public:
1792  using __type
1793  = typename __match_cv_qualifiers<_Tp, __unsigned_type>::__type;
1794  };
1795 
1796  // wchar_t, char8_t, char16_t and char32_t are integral types but are
1797  // neither signed integer types nor unsigned integer types, so must be
1798  // transformed to the unsigned integer type with the smallest rank.
1799  // Use the partial specialization for enumeration types to do that.
1800 #ifdef __WCHAR_TYPE__
1801  template<>
1802  struct __make_unsigned<wchar_t>
1803  {
1804  using __type
1805  = typename __make_unsigned_selector<wchar_t, false, true>::__type;
1806  };
1807 #endif
1808 
1809 #ifdef _GLIBCXX_USE_CHAR8_T
1810  template<>
1811  struct __make_unsigned<char8_t>
1812  {
1813  using __type
1814  = typename __make_unsigned_selector<char8_t, false, true>::__type;
1815  };
1816 #endif
1817 
1818  template<>
1819  struct __make_unsigned<char16_t>
1820  {
1821  using __type
1822  = typename __make_unsigned_selector<char16_t, false, true>::__type;
1823  };
1824 
1825  template<>
1826  struct __make_unsigned<char32_t>
1827  {
1828  using __type
1829  = typename __make_unsigned_selector<char32_t, false, true>::__type;
1830  };
1831  /// @endcond
1832 
1833  // Given an integral/enum type, return the corresponding unsigned
1834  // integer type.
1835  // Primary template.
1836  /// make_unsigned
1837  template<typename _Tp>
1839  { typedef typename __make_unsigned_selector<_Tp>::__type type; };
1840 
1841  // Integral, but don't define.
1842  template<>
1843  struct make_unsigned<bool>;
1844 
1845  /// @cond undocumented
1846 
1847  // Utility for finding the signed versions of unsigned integral types.
1848  template<typename _Tp>
1849  struct __make_signed
1850  { typedef _Tp __type; };
1851 
1852  template<>
1853  struct __make_signed<char>
1854  { typedef signed char __type; };
1855 
1856  template<>
1857  struct __make_signed<unsigned char>
1858  { typedef signed char __type; };
1859 
1860  template<>
1861  struct __make_signed<unsigned short>
1862  { typedef signed short __type; };
1863 
1864  template<>
1865  struct __make_signed<unsigned int>
1866  { typedef signed int __type; };
1867 
1868  template<>
1869  struct __make_signed<unsigned long>
1870  { typedef signed long __type; };
1871 
1872  template<>
1873  struct __make_signed<unsigned long long>
1874  { typedef signed long long __type; };
1875 
1876 #if defined(__GLIBCXX_TYPE_INT_N_0)
1877  template<>
1878  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_0>
1879  { typedef __GLIBCXX_TYPE_INT_N_0 __type; };
1880 #endif
1881 #if defined(__GLIBCXX_TYPE_INT_N_1)
1882  template<>
1883  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_1>
1884  { typedef __GLIBCXX_TYPE_INT_N_1 __type; };
1885 #endif
1886 #if defined(__GLIBCXX_TYPE_INT_N_2)
1887  template<>
1888  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_2>
1889  { typedef __GLIBCXX_TYPE_INT_N_2 __type; };
1890 #endif
1891 #if defined(__GLIBCXX_TYPE_INT_N_3)
1892  template<>
1893  struct __make_signed<unsigned __GLIBCXX_TYPE_INT_N_3>
1894  { typedef __GLIBCXX_TYPE_INT_N_3 __type; };
1895 #endif
1896 
1897  // Select between integral and enum: not possible to be both.
1898  template<typename _Tp,
1899  bool _IsInt = is_integral<_Tp>::value,
1900  bool _IsEnum = is_enum<_Tp>::value>
1901  class __make_signed_selector;
1902 
1903  template<typename _Tp>
1904  class __make_signed_selector<_Tp, true, false>
1905  {
1906  using __signed_type
1907  = typename __make_signed<__remove_cv_t<_Tp>>::__type;
1908 
1909  public:
1910  using __type
1911  = typename __match_cv_qualifiers<_Tp, __signed_type>::__type;
1912  };
1913 
1914  // Choose signed integer type with the smallest rank and same size as _Tp
1915  template<typename _Tp>
1916  class __make_signed_selector<_Tp, false, true>
1917  {
1918  typedef typename __make_unsigned_selector<_Tp>::__type __unsigned_type;
1919 
1920  public:
1921  typedef typename __make_signed_selector<__unsigned_type>::__type __type;
1922  };
1923 
1924  // wchar_t, char16_t and char32_t are integral types but are neither
1925  // signed integer types nor unsigned integer types, so must be
1926  // transformed to the signed integer type with the smallest rank.
1927  // Use the partial specialization for enumeration types to do that.
1928 #if defined(__WCHAR_TYPE__)
1929  template<>
1930  struct __make_signed<wchar_t>
1931  {
1932  using __type
1933  = typename __make_signed_selector<wchar_t, false, true>::__type;
1934  };
1935 #endif
1936 
1937 #if defined(_GLIBCXX_USE_CHAR8_T)
1938  template<>
1939  struct __make_signed<char8_t>
1940  {
1941  using __type
1942  = typename __make_signed_selector<char8_t, false, true>::__type;
1943  };
1944 #endif
1945 
1946  template<>
1947  struct __make_signed<char16_t>
1948  {
1949  using __type
1950  = typename __make_signed_selector<char16_t, false, true>::__type;
1951  };
1952 
1953  template<>
1954  struct __make_signed<char32_t>
1955  {
1956  using __type
1957  = typename __make_signed_selector<char32_t, false, true>::__type;
1958  };
1959  /// @endcond
1960 
1961  // Given an integral/enum type, return the corresponding signed
1962  // integer type.
1963  // Primary template.
1964  /// make_signed
1965  template<typename _Tp>
1967  { typedef typename __make_signed_selector<_Tp>::__type type; };
1968 
1969  // Integral, but don't define.
1970  template<>
1971  struct make_signed<bool>;
1972 
1973 #if __cplusplus > 201103L
1974  /// Alias template for make_signed
1975  template<typename _Tp>
1976  using make_signed_t = typename make_signed<_Tp>::type;
1977 
1978  /// Alias template for make_unsigned
1979  template<typename _Tp>
1980  using make_unsigned_t = typename make_unsigned<_Tp>::type;
1981 #endif
1982 
1983  // Array modifications.
1984 
1985  /// remove_extent
1986  template<typename _Tp>
1988  { typedef _Tp type; };
1989 
1990  template<typename _Tp, std::size_t _Size>
1991  struct remove_extent<_Tp[_Size]>
1992  { typedef _Tp type; };
1993 
1994  template<typename _Tp>
1995  struct remove_extent<_Tp[]>
1996  { typedef _Tp type; };
1997 
1998  /// remove_all_extents
1999  template<typename _Tp>
2001  { typedef _Tp type; };
2002 
2003  template<typename _Tp, std::size_t _Size>
2004  struct remove_all_extents<_Tp[_Size]>
2005  { typedef typename remove_all_extents<_Tp>::type type; };
2006 
2007  template<typename _Tp>
2008  struct remove_all_extents<_Tp[]>
2009  { typedef typename remove_all_extents<_Tp>::type type; };
2010 
2011 #if __cplusplus > 201103L
2012  /// Alias template for remove_extent
2013  template<typename _Tp>
2014  using remove_extent_t = typename remove_extent<_Tp>::type;
2015 
2016  /// Alias template for remove_all_extents
2017  template<typename _Tp>
2018  using remove_all_extents_t = typename remove_all_extents<_Tp>::type;
2019 #endif
2020 
2021  // Pointer modifications.
2022 
2023  template<typename _Tp, typename>
2024  struct __remove_pointer_helper
2025  { typedef _Tp type; };
2026 
2027  template<typename _Tp, typename _Up>
2028  struct __remove_pointer_helper<_Tp, _Up*>
2029  { typedef _Up type; };
2030 
2031  /// remove_pointer
2032  template<typename _Tp>
2034  : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
2035  { };
2036 
2037  template<typename _Tp, bool = __or_<__is_referenceable<_Tp>,
2038  is_void<_Tp>>::value>
2039  struct __add_pointer_helper
2040  { typedef _Tp type; };
2041 
2042  template<typename _Tp>
2043  struct __add_pointer_helper<_Tp, true>
2044  { typedef typename remove_reference<_Tp>::type* type; };
2045 
2046  /// add_pointer
2047  template<typename _Tp>
2049  : public __add_pointer_helper<_Tp>
2050  { };
2051 
2052 #if __cplusplus > 201103L
2053  /// Alias template for remove_pointer
2054  template<typename _Tp>
2055  using remove_pointer_t = typename remove_pointer<_Tp>::type;
2056 
2057  /// Alias template for add_pointer
2058  template<typename _Tp>
2059  using add_pointer_t = typename add_pointer<_Tp>::type;
2060 #endif
2061 
2062  template<std::size_t _Len>
2063  struct __aligned_storage_msa
2064  {
2065  union __type
2066  {
2067  unsigned char __data[_Len];
2068  struct __attribute__((__aligned__)) { } __align;
2069  };
2070  };
2071 
2072  /**
2073  * @brief Alignment type.
2074  *
2075  * The value of _Align is a default-alignment which shall be the
2076  * most stringent alignment requirement for any C++ object type
2077  * whose size is no greater than _Len (3.9). The member typedef
2078  * type shall be a POD type suitable for use as uninitialized
2079  * storage for any object whose size is at most _Len and whose
2080  * alignment is a divisor of _Align.
2081  */
2082  template<std::size_t _Len, std::size_t _Align =
2083  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2085  {
2086  union type
2087  {
2088  unsigned char __data[_Len];
2089  struct __attribute__((__aligned__((_Align)))) { } __align;
2090  };
2091  };
2092 
2093  template <typename... _Types>
2094  struct __strictest_alignment
2095  {
2096  static const size_t _S_alignment = 0;
2097  static const size_t _S_size = 0;
2098  };
2099 
2100  template <typename _Tp, typename... _Types>
2101  struct __strictest_alignment<_Tp, _Types...>
2102  {
2103  static const size_t _S_alignment =
2104  alignof(_Tp) > __strictest_alignment<_Types...>::_S_alignment
2105  ? alignof(_Tp) : __strictest_alignment<_Types...>::_S_alignment;
2106  static const size_t _S_size =
2107  sizeof(_Tp) > __strictest_alignment<_Types...>::_S_size
2108  ? sizeof(_Tp) : __strictest_alignment<_Types...>::_S_size;
2109  };
2110 
2111  /**
2112  * @brief Provide aligned storage for types.
2113  *
2114  * [meta.trans.other]
2115  *
2116  * Provides aligned storage for any of the provided types of at
2117  * least size _Len.
2118  *
2119  * @see aligned_storage
2120  */
2121  template <size_t _Len, typename... _Types>
2123  {
2124  private:
2125  static_assert(sizeof...(_Types) != 0, "At least one type is required");
2126 
2127  using __strictest = __strictest_alignment<_Types...>;
2128  static const size_t _S_len = _Len > __strictest::_S_size
2129  ? _Len : __strictest::_S_size;
2130  public:
2131  /// The value of the strictest alignment of _Types.
2132  static const size_t alignment_value = __strictest::_S_alignment;
2133  /// The storage.
2135  };
2136 
2137  template <size_t _Len, typename... _Types>
2138  const size_t aligned_union<_Len, _Types...>::alignment_value;
2139 
2140  /// @cond undocumented
2141 
2142  // Decay trait for arrays and functions, used for perfect forwarding
2143  // in make_pair, make_tuple, etc.
2144  template<typename _Up,
2145  bool _IsArray = is_array<_Up>::value,
2146  bool _IsFunction = is_function<_Up>::value>
2147  struct __decay_selector;
2148 
2149  // NB: DR 705.
2150  template<typename _Up>
2151  struct __decay_selector<_Up, false, false>
2152  { typedef __remove_cv_t<_Up> __type; };
2153 
2154  template<typename _Up>
2155  struct __decay_selector<_Up, true, false>
2156  { typedef typename remove_extent<_Up>::type* __type; };
2157 
2158  template<typename _Up>
2159  struct __decay_selector<_Up, false, true>
2160  { typedef typename add_pointer<_Up>::type __type; };
2161  /// @endcond
2162 
2163  /// decay
2164  template<typename _Tp>
2165  class decay
2166  {
2167  typedef typename remove_reference<_Tp>::type __remove_type;
2168 
2169  public:
2170  typedef typename __decay_selector<__remove_type>::__type type;
2171  };
2172 
2173  /// @cond undocumented
2174 
2175  // Helper which adds a reference to a type when given a reference_wrapper
2176  template<typename _Tp>
2177  struct __strip_reference_wrapper
2178  {
2179  typedef _Tp __type;
2180  };
2181 
2182  template<typename _Tp>
2183  struct __strip_reference_wrapper<reference_wrapper<_Tp> >
2184  {
2185  typedef _Tp& __type;
2186  };
2187 
2188  // __decay_t (std::decay_t for C++11).
2189  template<typename _Tp>
2190  using __decay_t = typename decay<_Tp>::type;
2191 
2192  template<typename _Tp>
2193  using __decay_and_strip = __strip_reference_wrapper<__decay_t<_Tp>>;
2194  /// @endcond
2195 
2196  // Primary template.
2197  /// Define a member typedef `type` only if a boolean constant is true.
2198  template<bool, typename _Tp = void>
2199  struct enable_if
2200  { };
2201 
2202  // Partial specialization for true.
2203  template<typename _Tp>
2204  struct enable_if<true, _Tp>
2205  { typedef _Tp type; };
2206 
2207  /// @cond undocumented
2208 
2209  // __enable_if_t (std::enable_if_t for C++11)
2210  template<bool _Cond, typename _Tp = void>
2211  using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
2212 
2213  // Helper for SFINAE constraints
2214  template<typename... _Cond>
2215  using _Require = __enable_if_t<__and_<_Cond...>::value>;
2216 
2217  // __remove_cvref_t (std::remove_cvref_t for C++11).
2218  template<typename _Tp>
2219  using __remove_cvref_t
2220  = typename remove_cv<typename remove_reference<_Tp>::type>::type;
2221  /// @endcond
2222 
2223  // Primary template.
2224  /// Define a member typedef @c type to one of two argument types.
2225  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2227  { typedef _Iftrue type; };
2228 
2229  // Partial specialization for false.
2230  template<typename _Iftrue, typename _Iffalse>
2231  struct conditional<false, _Iftrue, _Iffalse>
2232  { typedef _Iffalse type; };
2233 
2234  /// common_type
2235  template<typename... _Tp>
2236  struct common_type;
2237 
2238  // Sfinae-friendly common_type implementation:
2239 
2240  /// @cond undocumented
2241  struct __do_common_type_impl
2242  {
2243  template<typename _Tp, typename _Up>
2244  using __cond_t
2245  = decltype(true ? std::declval<_Tp>() : std::declval<_Up>());
2246 
2247  // if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2248  // denotes a valid type, let C denote that type.
2249  template<typename _Tp, typename _Up>
2250  static __success_type<__decay_t<__cond_t<_Tp, _Up>>>
2251  _S_test(int);
2252 
2253 #if __cplusplus > 201703L
2254  // Otherwise, if COND-RES(CREF(D1), CREF(D2)) denotes a type,
2255  // let C denote the type decay_t<COND-RES(CREF(D1), CREF(D2))>.
2256  template<typename _Tp, typename _Up>
2257  static __success_type<__remove_cvref_t<__cond_t<const _Tp&, const _Up&>>>
2258  _S_test_2(int);
2259 #endif
2260 
2261  template<typename, typename>
2262  static __failure_type
2263  _S_test_2(...);
2264 
2265  template<typename _Tp, typename _Up>
2266  static decltype(_S_test_2<_Tp, _Up>(0))
2267  _S_test(...);
2268  };
2269 
2270  // If sizeof...(T) is zero, there shall be no member type.
2271  template<>
2272  struct common_type<>
2273  { };
2274 
2275  // If sizeof...(T) is one, the same type, if any, as common_type_t<T0, T0>.
2276  template<typename _Tp0>
2277  struct common_type<_Tp0>
2278  : public common_type<_Tp0, _Tp0>
2279  { };
2280 
2281  // If sizeof...(T) is two, ...
2282  template<typename _Tp1, typename _Tp2,
2283  typename _Dp1 = __decay_t<_Tp1>, typename _Dp2 = __decay_t<_Tp2>>
2284  struct __common_type_impl
2285  {
2286  // If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false,
2287  // let C denote the same type, if any, as common_type_t<D1, D2>.
2288  using type = common_type<_Dp1, _Dp2>;
2289  };
2290 
2291  template<typename _Tp1, typename _Tp2>
2292  struct __common_type_impl<_Tp1, _Tp2, _Tp1, _Tp2>
2293  : private __do_common_type_impl
2294  {
2295  // Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
2296  // denotes a valid type, let C denote that type.
2297  using type = decltype(_S_test<_Tp1, _Tp2>(0));
2298  };
2299 
2300  // If sizeof...(T) is two, ...
2301  template<typename _Tp1, typename _Tp2>
2302  struct common_type<_Tp1, _Tp2>
2303  : public __common_type_impl<_Tp1, _Tp2>::type
2304  { };
2305 
2306  template<typename...>
2307  struct __common_type_pack
2308  { };
2309 
2310  template<typename, typename, typename = void>
2311  struct __common_type_fold;
2312 
2313  // If sizeof...(T) is greater than two, ...
2314  template<typename _Tp1, typename _Tp2, typename... _Rp>
2315  struct common_type<_Tp1, _Tp2, _Rp...>
2316  : public __common_type_fold<common_type<_Tp1, _Tp2>,
2317  __common_type_pack<_Rp...>>
2318  { };
2319 
2320  // Let C denote the same type, if any, as common_type_t<T1, T2>.
2321  // If there is such a type C, type shall denote the same type, if any,
2322  // as common_type_t<C, R...>.
2323  template<typename _CTp, typename... _Rp>
2324  struct __common_type_fold<_CTp, __common_type_pack<_Rp...>,
2325  __void_t<typename _CTp::type>>
2326  : public common_type<typename _CTp::type, _Rp...>
2327  { };
2328 
2329  // Otherwise, there shall be no member type.
2330  template<typename _CTp, typename _Rp>
2331  struct __common_type_fold<_CTp, _Rp, void>
2332  { };
2333 
2334  template<typename _Tp, bool = is_enum<_Tp>::value>
2335  struct __underlying_type_impl
2336  {
2337  using type = __underlying_type(_Tp);
2338  };
2339 
2340  template<typename _Tp>
2341  struct __underlying_type_impl<_Tp, false>
2342  { };
2343  /// @endcond
2344 
2345  /// The underlying type of an enum.
2346  template<typename _Tp>
2348  : public __underlying_type_impl<_Tp>
2349  { };
2350 
2351  /// @cond undocumented
2352  template<typename _Tp>
2353  struct __declval_protector
2354  {
2355  static const bool __stop = false;
2356  };
2357  /// @endcond
2358 
2359  /** Utility to simplify expressions used in unevaluated operands
2360  * @since C++11
2361  * @ingroup utilities
2362  */
2363  template<typename _Tp>
2364  auto declval() noexcept -> decltype(__declval<_Tp>(0))
2365  {
2366  static_assert(__declval_protector<_Tp>::__stop,
2367  "declval() must not be used!");
2368  return __declval<_Tp>(0);
2369  }
2370 
2371  /// result_of
2372  template<typename _Signature>
2373  struct result_of;
2374 
2375  // Sfinae-friendly result_of implementation:
2376 
2377 #define __cpp_lib_result_of_sfinae 201210
2378 
2379  /// @cond undocumented
2380  struct __invoke_memfun_ref { };
2381  struct __invoke_memfun_deref { };
2382  struct __invoke_memobj_ref { };
2383  struct __invoke_memobj_deref { };
2384  struct __invoke_other { };
2385 
2386  // Associate a tag type with a specialization of __success_type.
2387  template<typename _Tp, typename _Tag>
2388  struct __result_of_success : __success_type<_Tp>
2389  { using __invoke_type = _Tag; };
2390 
2391  // [func.require] paragraph 1 bullet 1:
2392  struct __result_of_memfun_ref_impl
2393  {
2394  template<typename _Fp, typename _Tp1, typename... _Args>
2395  static __result_of_success<decltype(
2396  (std::declval<_Tp1>().*std::declval<_Fp>())(std::declval<_Args>()...)
2397  ), __invoke_memfun_ref> _S_test(int);
2398 
2399  template<typename...>
2400  static __failure_type _S_test(...);
2401  };
2402 
2403  template<typename _MemPtr, typename _Arg, typename... _Args>
2404  struct __result_of_memfun_ref
2405  : private __result_of_memfun_ref_impl
2406  {
2407  typedef decltype(_S_test<_MemPtr, _Arg, _Args...>(0)) type;
2408  };
2409 
2410  // [func.require] paragraph 1 bullet 2:
2411  struct __result_of_memfun_deref_impl
2412  {
2413  template<typename _Fp, typename _Tp1, typename... _Args>
2414  static __result_of_success<decltype(
2415  ((*std::declval<_Tp1>()).*std::declval<_Fp>())(std::declval<_Args>()...)
2416  ), __invoke_memfun_deref> _S_test(int);
2417 
2418  template<typename...>
2419  static __failure_type _S_test(...);
2420  };
2421 
2422  template<typename _MemPtr, typename _Arg, typename... _Args>
2423  struct __result_of_memfun_deref
2424  : private __result_of_memfun_deref_impl
2425  {
2426  typedef decltype(_S_test<_MemPtr, _Arg, _Args...>(0)) type;
2427  };
2428 
2429  // [func.require] paragraph 1 bullet 3:
2430  struct __result_of_memobj_ref_impl
2431  {
2432  template<typename _Fp, typename _Tp1>
2433  static __result_of_success<decltype(
2434  std::declval<_Tp1>().*std::declval<_Fp>()
2435  ), __invoke_memobj_ref> _S_test(int);
2436 
2437  template<typename, typename>
2438  static __failure_type _S_test(...);
2439  };
2440 
2441  template<typename _MemPtr, typename _Arg>
2442  struct __result_of_memobj_ref
2443  : private __result_of_memobj_ref_impl
2444  {
2445  typedef decltype(_S_test<_MemPtr, _Arg>(0)) type;
2446  };
2447 
2448  // [func.require] paragraph 1 bullet 4:
2449  struct __result_of_memobj_deref_impl
2450  {
2451  template<typename _Fp, typename _Tp1>
2452  static __result_of_success<decltype(
2453  (*std::declval<_Tp1>()).*std::declval<_Fp>()
2454  ), __invoke_memobj_deref> _S_test(int);
2455 
2456  template<typename, typename>
2457  static __failure_type _S_test(...);
2458  };
2459 
2460  template<typename _MemPtr, typename _Arg>
2461  struct __result_of_memobj_deref
2462  : private __result_of_memobj_deref_impl
2463  {
2464  typedef decltype(_S_test<_MemPtr, _Arg>(0)) type;
2465  };
2466 
2467  template<typename _MemPtr, typename _Arg>
2468  struct __result_of_memobj;
2469 
2470  template<typename _Res, typename _Class, typename _Arg>
2471  struct __result_of_memobj<_Res _Class::*, _Arg>
2472  {
2473  typedef __remove_cvref_t<_Arg> _Argval;
2474  typedef _Res _Class::* _MemPtr;
2475  typedef typename conditional<__or_<is_same<_Argval, _Class>,
2476  is_base_of<_Class, _Argval>>::value,
2477  __result_of_memobj_ref<_MemPtr, _Arg>,
2478  __result_of_memobj_deref<_MemPtr, _Arg>
2479  >::type::type type;
2480  };
2481 
2482  template<typename _MemPtr, typename _Arg, typename... _Args>
2483  struct __result_of_memfun;
2484 
2485  template<typename _Res, typename _Class, typename _Arg, typename... _Args>
2486  struct __result_of_memfun<_Res _Class::*, _Arg, _Args...>
2487  {
2488  typedef typename remove_reference<_Arg>::type _Argval;
2489  typedef _Res _Class::* _MemPtr;
2490  typedef typename conditional<is_base_of<_Class, _Argval>::value,
2491  __result_of_memfun_ref<_MemPtr, _Arg, _Args...>,
2492  __result_of_memfun_deref<_MemPtr, _Arg, _Args...>
2493  >::type::type type;
2494  };
2495 
2496  // _GLIBCXX_RESOLVE_LIB_DEFECTS
2497  // 2219. INVOKE-ing a pointer to member with a reference_wrapper
2498  // as the object expression
2499 
2500  // Used by result_of, invoke etc. to unwrap a reference_wrapper.
2501  template<typename _Tp, typename _Up = __remove_cvref_t<_Tp>>
2502  struct __inv_unwrap
2503  {
2504  using type = _Tp;
2505  };
2506 
2507  template<typename _Tp, typename _Up>
2508  struct __inv_unwrap<_Tp, reference_wrapper<_Up>>
2509  {
2510  using type = _Up&;
2511  };
2512 
2513  template<bool, bool, typename _Functor, typename... _ArgTypes>
2514  struct __result_of_impl
2515  {
2516  typedef __failure_type type;
2517  };
2518 
2519  template<typename _MemPtr, typename _Arg>
2520  struct __result_of_impl<true, false, _MemPtr, _Arg>
2521  : public __result_of_memobj<__decay_t<_MemPtr>,
2522  typename __inv_unwrap<_Arg>::type>
2523  { };
2524 
2525  template<typename _MemPtr, typename _Arg, typename... _Args>
2526  struct __result_of_impl<false, true, _MemPtr, _Arg, _Args...>
2527  : public __result_of_memfun<__decay_t<_MemPtr>,
2528  typename __inv_unwrap<_Arg>::type, _Args...>
2529  { };
2530 
2531  // [func.require] paragraph 1 bullet 5:
2532  struct __result_of_other_impl
2533  {
2534  template<typename _Fn, typename... _Args>
2535  static __result_of_success<decltype(
2536  std::declval<_Fn>()(std::declval<_Args>()...)
2537  ), __invoke_other> _S_test(int);
2538 
2539  template<typename...>
2540  static __failure_type _S_test(...);
2541  };
2542 
2543  template<typename _Functor, typename... _ArgTypes>
2544  struct __result_of_impl<false, false, _Functor, _ArgTypes...>
2545  : private __result_of_other_impl
2546  {
2547  typedef decltype(_S_test<_Functor, _ArgTypes...>(0)) type;
2548  };
2549 
2550  // __invoke_result (std::invoke_result for C++11)
2551  template<typename _Functor, typename... _ArgTypes>
2552  struct __invoke_result
2553  : public __result_of_impl<
2554  is_member_object_pointer<
2555  typename remove_reference<_Functor>::type
2556  >::value,
2557  is_member_function_pointer<
2558  typename remove_reference<_Functor>::type
2559  >::value,
2560  _Functor, _ArgTypes...
2561  >::type
2562  { };
2563  /// @endcond
2564 
2565  template<typename _Functor, typename... _ArgTypes>
2566  struct result_of<_Functor(_ArgTypes...)>
2567  : public __invoke_result<_Functor, _ArgTypes...>
2568  { };
2569 
2570 #if __cplusplus >= 201402L
2571  /// Alias template for aligned_storage
2572  template<size_t _Len, size_t _Align =
2573  __alignof__(typename __aligned_storage_msa<_Len>::__type)>
2575 
2576  template <size_t _Len, typename... _Types>
2577  using aligned_union_t = typename aligned_union<_Len, _Types...>::type;
2578 
2579  /// Alias template for decay
2580  template<typename _Tp>
2581  using decay_t = typename decay<_Tp>::type;
2582 
2583  /// Alias template for enable_if
2584  template<bool _Cond, typename _Tp = void>
2586 
2587  /// Alias template for conditional
2588  template<bool _Cond, typename _Iftrue, typename _Iffalse>
2589  using conditional_t = typename conditional<_Cond, _Iftrue, _Iffalse>::type;
2590 
2591  /// Alias template for common_type
2592  template<typename... _Tp>
2593  using common_type_t = typename common_type<_Tp...>::type;
2594 
2595  /// Alias template for underlying_type
2596  template<typename _Tp>
2598 
2599  /// Alias template for result_of
2600  template<typename _Tp>
2602 #endif // C++14
2603 
2604 #if __cplusplus >= 201703L || !defined(__STRICT_ANSI__) // c++17 or gnu++11
2605 #define __cpp_lib_void_t 201411
2606  /// A metafunction that always yields void, used for detecting valid types.
2607  template<typename...> using void_t = void;
2608 #endif
2609 
2610  /// @cond undocumented
2611 
2612  /// Implementation of the detection idiom (negative case).
2613  template<typename _Default, typename _AlwaysVoid,
2614  template<typename...> class _Op, typename... _Args>
2615  struct __detector
2616  {
2617  using value_t = false_type;
2618  using type = _Default;
2619  };
2620 
2621  /// Implementation of the detection idiom (positive case).
2622  template<typename _Default, template<typename...> class _Op,
2623  typename... _Args>
2624  struct __detector<_Default, __void_t<_Op<_Args...>>, _Op, _Args...>
2625  {
2626  using value_t = true_type;
2627  using type = _Op<_Args...>;
2628  };
2629 
2630  // Detect whether _Op<_Args...> is a valid type, use _Default if not.
2631  template<typename _Default, template<typename...> class _Op,
2632  typename... _Args>
2633  using __detected_or = __detector<_Default, void, _Op, _Args...>;
2634 
2635  // _Op<_Args...> if that is a valid type, otherwise _Default.
2636  template<typename _Default, template<typename...> class _Op,
2637  typename... _Args>
2638  using __detected_or_t
2639  = typename __detected_or<_Default, _Op, _Args...>::type;
2640 
2641  /**
2642  * Use SFINAE to determine if the type _Tp has a publicly-accessible
2643  * member type _NTYPE.
2644  */
2645 #define _GLIBCXX_HAS_NESTED_TYPE(_NTYPE) \
2646  template<typename _Tp, typename = __void_t<>> \
2647  struct __has_##_NTYPE \
2648  : false_type \
2649  { }; \
2650  template<typename _Tp> \
2651  struct __has_##_NTYPE<_Tp, __void_t<typename _Tp::_NTYPE>> \
2652  : true_type \
2653  { };
2654 
2655  template <typename _Tp>
2656  struct __is_swappable;
2657 
2658  template <typename _Tp>
2659  struct __is_nothrow_swappable;
2660 
2661  template<typename>
2662  struct __is_tuple_like_impl : false_type
2663  { };
2664 
2665  template<typename... _Tps>
2666  struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
2667  { };
2668 
2669  // Internal type trait that allows us to sfinae-protect tuple_cat.
2670  template<typename _Tp>
2671  struct __is_tuple_like
2672  : public __is_tuple_like_impl<__remove_cvref_t<_Tp>>::type
2673  { };
2674  /// @endcond
2675 
2676  template<typename _Tp>
2677  _GLIBCXX20_CONSTEXPR
2678  inline
2679  _Require<__not_<__is_tuple_like<_Tp>>,
2680  is_move_constructible<_Tp>,
2681  is_move_assignable<_Tp>>
2682  swap(_Tp&, _Tp&)
2683  noexcept(__and_<is_nothrow_move_constructible<_Tp>,
2684  is_nothrow_move_assignable<_Tp>>::value);
2685 
2686  template<typename _Tp, size_t _Nm>
2687  _GLIBCXX20_CONSTEXPR
2688  inline
2689  __enable_if_t<__is_swappable<_Tp>::value>
2690  swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
2691  noexcept(__is_nothrow_swappable<_Tp>::value);
2692 
2693  /// @cond undocumented
2694  namespace __swappable_details {
2695  using std::swap;
2696 
2697  struct __do_is_swappable_impl
2698  {
2699  template<typename _Tp, typename
2700  = decltype(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))>
2701  static true_type __test(int);
2702 
2703  template<typename>
2704  static false_type __test(...);
2705  };
2706 
2707  struct __do_is_nothrow_swappable_impl
2708  {
2709  template<typename _Tp>
2710  static __bool_constant<
2711  noexcept(swap(std::declval<_Tp&>(), std::declval<_Tp&>()))
2712  > __test(int);
2713 
2714  template<typename>
2715  static false_type __test(...);
2716  };
2717 
2718  } // namespace __swappable_details
2719 
2720  template<typename _Tp>
2721  struct __is_swappable_impl
2722  : public __swappable_details::__do_is_swappable_impl
2723  {
2724  typedef decltype(__test<_Tp>(0)) type;
2725  };
2726 
2727  template<typename _Tp>
2728  struct __is_nothrow_swappable_impl
2729  : public __swappable_details::__do_is_nothrow_swappable_impl
2730  {
2731  typedef decltype(__test<_Tp>(0)) type;
2732  };
2733 
2734  template<typename _Tp>
2735  struct __is_swappable
2736  : public __is_swappable_impl<_Tp>::type
2737  { };
2738 
2739  template<typename _Tp>
2740  struct __is_nothrow_swappable
2741  : public __is_nothrow_swappable_impl<_Tp>::type
2742  { };
2743  /// @endcond
2744 
2745 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
2746 #define __cpp_lib_is_swappable 201603
2747  /// Metafunctions used for detecting swappable types: p0185r1
2748 
2749  /// is_swappable
2750  template<typename _Tp>
2752  : public __is_swappable_impl<_Tp>::type
2753  {
2754  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2755  "template argument must be a complete class or an unbounded array");
2756  };
2757 
2758  /// is_nothrow_swappable
2759  template<typename _Tp>
2761  : public __is_nothrow_swappable_impl<_Tp>::type
2762  {
2763  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2764  "template argument must be a complete class or an unbounded array");
2765  };
2766 
2767 #if __cplusplus >= 201402L
2768  /// is_swappable_v
2769  template<typename _Tp>
2770  _GLIBCXX17_INLINE constexpr bool is_swappable_v =
2772 
2773  /// is_nothrow_swappable_v
2774  template<typename _Tp>
2775  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_v =
2777 #endif // __cplusplus >= 201402L
2778 
2779  /// @cond undocumented
2780  namespace __swappable_with_details {
2781  using std::swap;
2782 
2783  struct __do_is_swappable_with_impl
2784  {
2785  template<typename _Tp, typename _Up, typename
2786  = decltype(swap(std::declval<_Tp>(), std::declval<_Up>())),
2787  typename
2788  = decltype(swap(std::declval<_Up>(), std::declval<_Tp>()))>
2789  static true_type __test(int);
2790 
2791  template<typename, typename>
2792  static false_type __test(...);
2793  };
2794 
2795  struct __do_is_nothrow_swappable_with_impl
2796  {
2797  template<typename _Tp, typename _Up>
2798  static __bool_constant<
2799  noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()))
2800  &&
2801  noexcept(swap(std::declval<_Up>(), std::declval<_Tp>()))
2802  > __test(int);
2803 
2804  template<typename, typename>
2805  static false_type __test(...);
2806  };
2807 
2808  } // namespace __swappable_with_details
2809 
2810  template<typename _Tp, typename _Up>
2811  struct __is_swappable_with_impl
2812  : public __swappable_with_details::__do_is_swappable_with_impl
2813  {
2814  typedef decltype(__test<_Tp, _Up>(0)) type;
2815  };
2816 
2817  // Optimization for the homogenous lvalue case, not required:
2818  template<typename _Tp>
2819  struct __is_swappable_with_impl<_Tp&, _Tp&>
2820  : public __swappable_details::__do_is_swappable_impl
2821  {
2822  typedef decltype(__test<_Tp&>(0)) type;
2823  };
2824 
2825  template<typename _Tp, typename _Up>
2826  struct __is_nothrow_swappable_with_impl
2827  : public __swappable_with_details::__do_is_nothrow_swappable_with_impl
2828  {
2829  typedef decltype(__test<_Tp, _Up>(0)) type;
2830  };
2831 
2832  // Optimization for the homogenous lvalue case, not required:
2833  template<typename _Tp>
2834  struct __is_nothrow_swappable_with_impl<_Tp&, _Tp&>
2835  : public __swappable_details::__do_is_nothrow_swappable_impl
2836  {
2837  typedef decltype(__test<_Tp&>(0)) type;
2838  };
2839  /// @endcond
2840 
2841  /// is_swappable_with
2842  template<typename _Tp, typename _Up>
2844  : public __is_swappable_with_impl<_Tp, _Up>::type
2845  {
2846  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2847  "first template argument must be a complete class or an unbounded array");
2848  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2849  "second template argument must be a complete class or an unbounded array");
2850  };
2851 
2852  /// is_nothrow_swappable_with
2853  template<typename _Tp, typename _Up>
2855  : public __is_nothrow_swappable_with_impl<_Tp, _Up>::type
2856  {
2857  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
2858  "first template argument must be a complete class or an unbounded array");
2859  static_assert(std::__is_complete_or_unbounded(__type_identity<_Up>{}),
2860  "second template argument must be a complete class or an unbounded array");
2861  };
2862 
2863 #if __cplusplus >= 201402L
2864  /// is_swappable_with_v
2865  template<typename _Tp, typename _Up>
2866  _GLIBCXX17_INLINE constexpr bool is_swappable_with_v =
2868 
2869  /// is_nothrow_swappable_with_v
2870  template<typename _Tp, typename _Up>
2871  _GLIBCXX17_INLINE constexpr bool is_nothrow_swappable_with_v =
2873 #endif // __cplusplus >= 201402L
2874 
2875 #endif// c++1z or gnu++11
2876 
2877  /// @cond undocumented
2878 
2879  // __is_invocable (std::is_invocable for C++11)
2880 
2881  // The primary template is used for invalid INVOKE expressions.
2882  template<typename _Result, typename _Ret,
2883  bool = is_void<_Ret>::value, typename = void>
2884  struct __is_invocable_impl : false_type { };
2885 
2886  // Used for valid INVOKE and INVOKE<void> expressions.
2887  template<typename _Result, typename _Ret>
2888  struct __is_invocable_impl<_Result, _Ret,
2889  /* is_void<_Ret> = */ true,
2890  __void_t<typename _Result::type>>
2891  : true_type
2892  { };
2893 
2894 #pragma GCC diagnostic push
2895 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
2896  // Used for INVOKE<R> expressions to check the implicit conversion to R.
2897  template<typename _Result, typename _Ret>
2898  struct __is_invocable_impl<_Result, _Ret,
2899  /* is_void<_Ret> = */ false,
2900  __void_t<typename _Result::type>>
2901  {
2902  private:
2903  // The type of the INVOKE expression.
2904  // Unlike declval, this doesn't add_rvalue_reference.
2905  static typename _Result::type _S_get();
2906 
2907  template<typename _Tp>
2908  static void _S_conv(_Tp);
2909 
2910  // This overload is viable if INVOKE(f, args...) can convert to _Tp.
2911  template<typename _Tp, typename = decltype(_S_conv<_Tp>(_S_get()))>
2912  static true_type
2913  _S_test(int);
2914 
2915  template<typename _Tp>
2916  static false_type
2917  _S_test(...);
2918 
2919  public:
2920  using type = decltype(_S_test<_Ret>(1));
2921  };
2922 #pragma GCC diagnostic pop
2923 
2924  template<typename _Fn, typename... _ArgTypes>
2925  struct __is_invocable
2926  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
2927  { };
2928 
2929  template<typename _Fn, typename _Tp, typename... _Args>
2930  constexpr bool __call_is_nt(__invoke_memfun_ref)
2931  {
2932  using _Up = typename __inv_unwrap<_Tp>::type;
2933  return noexcept((std::declval<_Up>().*std::declval<_Fn>())(
2934  std::declval<_Args>()...));
2935  }
2936 
2937  template<typename _Fn, typename _Tp, typename... _Args>
2938  constexpr bool __call_is_nt(__invoke_memfun_deref)
2939  {
2940  return noexcept(((*std::declval<_Tp>()).*std::declval<_Fn>())(
2941  std::declval<_Args>()...));
2942  }
2943 
2944  template<typename _Fn, typename _Tp>
2945  constexpr bool __call_is_nt(__invoke_memobj_ref)
2946  {
2947  using _Up = typename __inv_unwrap<_Tp>::type;
2948  return noexcept(std::declval<_Up>().*std::declval<_Fn>());
2949  }
2950 
2951  template<typename _Fn, typename _Tp>
2952  constexpr bool __call_is_nt(__invoke_memobj_deref)
2953  {
2954  return noexcept((*std::declval<_Tp>()).*std::declval<_Fn>());
2955  }
2956 
2957  template<typename _Fn, typename... _Args>
2958  constexpr bool __call_is_nt(__invoke_other)
2959  {
2960  return noexcept(std::declval<_Fn>()(std::declval<_Args>()...));
2961  }
2962 
2963  template<typename _Result, typename _Fn, typename... _Args>
2964  struct __call_is_nothrow
2965  : __bool_constant<
2966  std::__call_is_nt<_Fn, _Args...>(typename _Result::__invoke_type{})
2967  >
2968  { };
2969 
2970  template<typename _Fn, typename... _Args>
2971  using __call_is_nothrow_
2972  = __call_is_nothrow<__invoke_result<_Fn, _Args...>, _Fn, _Args...>;
2973 
2974  // __is_nothrow_invocable (std::is_nothrow_invocable for C++11)
2975  template<typename _Fn, typename... _Args>
2976  struct __is_nothrow_invocable
2977  : __and_<__is_invocable<_Fn, _Args...>,
2978  __call_is_nothrow_<_Fn, _Args...>>::type
2979  { };
2980 
2981 #pragma GCC diagnostic push
2982 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
2983  struct __nonesuchbase {};
2984  struct __nonesuch : private __nonesuchbase {
2985  ~__nonesuch() = delete;
2986  __nonesuch(__nonesuch const&) = delete;
2987  void operator=(__nonesuch const&) = delete;
2988  };
2989 #pragma GCC diagnostic pop
2990  /// @endcond
2991 
2992 #if __cplusplus >= 201703L
2993 # define __cpp_lib_is_invocable 201703
2994 
2995  /// std::invoke_result
2996  template<typename _Functor, typename... _ArgTypes>
2998  : public __invoke_result<_Functor, _ArgTypes...>
2999  {
3000  static_assert(std::__is_complete_or_unbounded(__type_identity<_Functor>{}),
3001  "_Functor must be a complete class or an unbounded array");
3002  static_assert((std::__is_complete_or_unbounded(
3003  __type_identity<_ArgTypes>{}) && ...),
3004  "each argument type must be a complete class or an unbounded array");
3005  };
3006 
3007  /// std::invoke_result_t
3008  template<typename _Fn, typename... _Args>
3009  using invoke_result_t = typename invoke_result<_Fn, _Args...>::type;
3010 
3011  /// std::is_invocable
3012  template<typename _Fn, typename... _ArgTypes>
3014  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>::type
3015  {
3016  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3017  "_Fn must be a complete class or an unbounded array");
3018  static_assert((std::__is_complete_or_unbounded(
3019  __type_identity<_ArgTypes>{}) && ...),
3020  "each argument type must be a complete class or an unbounded array");
3021  };
3022 
3023  /// std::is_invocable_r
3024  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3026  : __is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>::type
3027  {
3028  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3029  "_Fn must be a complete class or an unbounded array");
3030  static_assert((std::__is_complete_or_unbounded(
3031  __type_identity<_ArgTypes>{}) && ...),
3032  "each argument type must be a complete class or an unbounded array");
3033  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3034  "_Ret must be a complete class or an unbounded array");
3035  };
3036 
3037  /// std::is_nothrow_invocable
3038  template<typename _Fn, typename... _ArgTypes>
3040  : __and_<__is_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, void>,
3041  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3042  {
3043  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3044  "_Fn must be a complete class or an unbounded array");
3045  static_assert((std::__is_complete_or_unbounded(
3046  __type_identity<_ArgTypes>{}) && ...),
3047  "each argument type must be a complete class or an unbounded array");
3048  };
3049 
3050  /// @cond undocumented
3051  template<typename _Result, typename _Ret, typename = void>
3052  struct __is_nt_invocable_impl : false_type { };
3053 
3054  template<typename _Result, typename _Ret>
3055  struct __is_nt_invocable_impl<_Result, _Ret,
3056  __void_t<typename _Result::type>>
3057  : __or_<is_void<_Ret>,
3058  __is_nothrow_convertible<typename _Result::type, _Ret>>
3059  { };
3060  /// @endcond
3061 
3062  /// std::is_nothrow_invocable_r
3063  template<typename _Ret, typename _Fn, typename... _ArgTypes>
3065  : __and_<__is_nt_invocable_impl<__invoke_result<_Fn, _ArgTypes...>, _Ret>,
3066  __call_is_nothrow_<_Fn, _ArgTypes...>>::type
3067  {
3068  static_assert(std::__is_complete_or_unbounded(__type_identity<_Fn>{}),
3069  "_Fn must be a complete class or an unbounded array");
3070  static_assert((std::__is_complete_or_unbounded(
3071  __type_identity<_ArgTypes>{}) && ...),
3072  "each argument type must be a complete class or an unbounded array");
3073  static_assert(std::__is_complete_or_unbounded(__type_identity<_Ret>{}),
3074  "_Ret must be a complete class or an unbounded array");
3075  };
3076 #endif // C++17
3077 
3078 #if __cplusplus >= 201703L
3079 # define __cpp_lib_type_trait_variable_templates 201510L
3080  /**
3081  * @defgroup variable_templates Variable templates for type traits.
3082  * @ingroup metaprogramming
3083  *
3084  * The variable `is_foo_v<T>` is a boolean constant with the same value
3085  * as the type trait `is_foo<T>::value`.
3086  *
3087  * @since C++17
3088  */
3089 
3090  /** @ingroup variable_templates
3091  * @{
3092  */
3093 template <typename _Tp>
3094  inline constexpr bool is_void_v = is_void<_Tp>::value;
3095 template <typename _Tp>
3096  inline constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value;
3097 template <typename _Tp>
3098  inline constexpr bool is_integral_v = is_integral<_Tp>::value;
3099 template <typename _Tp>
3100  inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
3101 template <typename _Tp>
3102  inline constexpr bool is_array_v = is_array<_Tp>::value;
3103 template <typename _Tp>
3104  inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
3105 template <typename _Tp>
3106  inline constexpr bool is_lvalue_reference_v =
3108 template <typename _Tp>
3109  inline constexpr bool is_rvalue_reference_v =
3111 template <typename _Tp>
3112  inline constexpr bool is_member_object_pointer_v =
3114 template <typename _Tp>
3115  inline constexpr bool is_member_function_pointer_v =
3117 template <typename _Tp>
3118  inline constexpr bool is_enum_v = is_enum<_Tp>::value;
3119 template <typename _Tp>
3120  inline constexpr bool is_union_v = is_union<_Tp>::value;
3121 template <typename _Tp>
3122  inline constexpr bool is_class_v = is_class<_Tp>::value;
3123 template <typename _Tp>
3124  inline constexpr bool is_function_v = is_function<_Tp>::value;
3125 template <typename _Tp>
3126  inline constexpr bool is_reference_v = is_reference<_Tp>::value;
3127 template <typename _Tp>
3128  inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
3129 template <typename _Tp>
3130  inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
3131 template <typename _Tp>
3132  inline constexpr bool is_object_v = is_object<_Tp>::value;
3133 template <typename _Tp>
3134  inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
3135 template <typename _Tp>
3136  inline constexpr bool is_compound_v = is_compound<_Tp>::value;
3137 template <typename _Tp>
3138  inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
3139 template <typename _Tp>
3140  inline constexpr bool is_const_v = is_const<_Tp>::value;
3141 template <typename _Tp>
3142  inline constexpr bool is_volatile_v = is_volatile<_Tp>::value;
3143 template <typename _Tp>
3144  inline constexpr bool is_trivial_v = is_trivial<_Tp>::value;
3145 template <typename _Tp>
3146  inline constexpr bool is_trivially_copyable_v =
3148 template <typename _Tp>
3149  inline constexpr bool is_standard_layout_v = is_standard_layout<_Tp>::value;
3150 #pragma GCC diagnostic push
3151 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
3152 template <typename _Tp>
3153  _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
3154  inline constexpr bool is_pod_v = is_pod<_Tp>::value;
3155 template <typename _Tp>
3156  _GLIBCXX17_DEPRECATED
3157  inline constexpr bool is_literal_type_v = is_literal_type<_Tp>::value;
3158 #pragma GCC diagnostic pop
3159  template <typename _Tp>
3160  inline constexpr bool is_empty_v = is_empty<_Tp>::value;
3161 template <typename _Tp>
3162  inline constexpr bool is_polymorphic_v = is_polymorphic<_Tp>::value;
3163 template <typename _Tp>
3164  inline constexpr bool is_abstract_v = is_abstract<_Tp>::value;
3165 template <typename _Tp>
3166  inline constexpr bool is_final_v = is_final<_Tp>::value;
3167 template <typename _Tp>
3168  inline constexpr bool is_signed_v = is_signed<_Tp>::value;
3169 template <typename _Tp>
3170  inline constexpr bool is_unsigned_v = is_unsigned<_Tp>::value;
3171 template <typename _Tp, typename... _Args>
3172  inline constexpr bool is_constructible_v =
3173  is_constructible<_Tp, _Args...>::value;
3174 template <typename _Tp>
3175  inline constexpr bool is_default_constructible_v =
3177 template <typename _Tp>
3178  inline constexpr bool is_copy_constructible_v =
3180 template <typename _Tp>
3181  inline constexpr bool is_move_constructible_v =
3183 template <typename _Tp, typename _Up>
3184  inline constexpr bool is_assignable_v = is_assignable<_Tp, _Up>::value;
3185 template <typename _Tp>
3186  inline constexpr bool is_copy_assignable_v = is_copy_assignable<_Tp>::value;
3187 template <typename _Tp>
3188  inline constexpr bool is_move_assignable_v = is_move_assignable<_Tp>::value;
3189 template <typename _Tp>
3190  inline constexpr bool is_destructible_v = is_destructible<_Tp>::value;
3191 template <typename _Tp, typename... _Args>
3192  inline constexpr bool is_trivially_constructible_v =
3193  is_trivially_constructible<_Tp, _Args...>::value;
3194 template <typename _Tp>
3195  inline constexpr bool is_trivially_default_constructible_v =
3197 template <typename _Tp>
3198  inline constexpr bool is_trivially_copy_constructible_v =
3200 template <typename _Tp>
3201  inline constexpr bool is_trivially_move_constructible_v =
3203 template <typename _Tp, typename _Up>
3204  inline constexpr bool is_trivially_assignable_v =
3206 template <typename _Tp>
3207  inline constexpr bool is_trivially_copy_assignable_v =
3209 template <typename _Tp>
3210  inline constexpr bool is_trivially_move_assignable_v =
3212 template <typename _Tp>
3213  inline constexpr bool is_trivially_destructible_v =
3215 template <typename _Tp, typename... _Args>
3216  inline constexpr bool is_nothrow_constructible_v =
3217  is_nothrow_constructible<_Tp, _Args...>::value;
3218 template <typename _Tp>
3219  inline constexpr bool is_nothrow_default_constructible_v =
3221 template <typename _Tp>
3222  inline constexpr bool is_nothrow_copy_constructible_v =
3224 template <typename _Tp>
3225  inline constexpr bool is_nothrow_move_constructible_v =
3227 template <typename _Tp, typename _Up>
3228  inline constexpr bool is_nothrow_assignable_v =
3230 template <typename _Tp>
3231  inline constexpr bool is_nothrow_copy_assignable_v =
3233 template <typename _Tp>
3234  inline constexpr bool is_nothrow_move_assignable_v =
3236 template <typename _Tp>
3237  inline constexpr bool is_nothrow_destructible_v =
3239 template <typename _Tp>
3240  inline constexpr bool has_virtual_destructor_v =
3242 template <typename _Tp>
3243  inline constexpr size_t alignment_of_v = alignment_of<_Tp>::value;
3244 template <typename _Tp>
3245  inline constexpr size_t rank_v = rank<_Tp>::value;
3246 template <typename _Tp, unsigned _Idx = 0>
3247  inline constexpr size_t extent_v = extent<_Tp, _Idx>::value;
3248 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
3249 template <typename _Tp, typename _Up>
3250  inline constexpr bool is_same_v = __is_same(_Tp, _Up);
3251 #else
3252 template <typename _Tp, typename _Up>
3253  inline constexpr bool is_same_v = std::is_same<_Tp, _Up>::value;
3254 #endif
3255 template <typename _Base, typename _Derived>
3256  inline constexpr bool is_base_of_v = is_base_of<_Base, _Derived>::value;
3257 template <typename _From, typename _To>
3258  inline constexpr bool is_convertible_v = is_convertible<_From, _To>::value;
3259 template<typename _Fn, typename... _Args>
3260  inline constexpr bool is_invocable_v = is_invocable<_Fn, _Args...>::value;
3261 template<typename _Fn, typename... _Args>
3262  inline constexpr bool is_nothrow_invocable_v
3263  = is_nothrow_invocable<_Fn, _Args...>::value;
3264 template<typename _Ret, typename _Fn, typename... _Args>
3265  inline constexpr bool is_invocable_r_v
3266  = is_invocable_r<_Ret, _Fn, _Args...>::value;
3267 template<typename _Ret, typename _Fn, typename... _Args>
3268  inline constexpr bool is_nothrow_invocable_r_v
3269  = is_nothrow_invocable_r<_Ret, _Fn, _Args...>::value;
3270 /// @}
3271 
3272 #ifdef _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP
3273 # define __cpp_lib_has_unique_object_representations 201606
3274  /// has_unique_object_representations
3275  template<typename _Tp>
3276  struct has_unique_object_representations
3277  : bool_constant<__has_unique_object_representations(
3278  remove_cv_t<remove_all_extents_t<_Tp>>
3279  )>
3280  {
3281  static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
3282  "template argument must be a complete class or an unbounded array");
3283  };
3284 
3285  /// @ingroup variable_templates
3286  template<typename _Tp>
3287  inline constexpr bool has_unique_object_representations_v
3288  = has_unique_object_representations<_Tp>::value;
3289 #endif
3290 
3291 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE
3292 # define __cpp_lib_is_aggregate 201703
3293  /// is_aggregate
3294  template<typename _Tp>
3295  struct is_aggregate
3296  : bool_constant<__is_aggregate(remove_cv_t<_Tp>)>
3297  { };
3298 
3299  /// @ingroup variable_templates
3300  template<typename _Tp>
3301  inline constexpr bool is_aggregate_v = is_aggregate<_Tp>::value;
3302 #endif
3303 #endif // C++17
3304 
3305 #if __cplusplus > 201703L
3306 #define __cpp_lib_remove_cvref 201711L
3307 
3308  /// Remove references and cv-qualifiers.
3309  template<typename _Tp>
3310  struct remove_cvref
3311  : remove_cv<_Tp>
3312  { };
3313 
3314  template<typename _Tp>
3315  struct remove_cvref<_Tp&>
3316  : remove_cv<_Tp>
3317  { };
3318 
3319  template<typename _Tp>
3320  struct remove_cvref<_Tp&&>
3321  : remove_cv<_Tp>
3322  { };
3323 
3324  template<typename _Tp>
3325  using remove_cvref_t = typename remove_cvref<_Tp>::type;
3326 
3327 #define __cpp_lib_type_identity 201806L
3328  /// Identity metafunction.
3329  template<typename _Tp>
3330  struct type_identity { using type = _Tp; };
3331 
3332  template<typename _Tp>
3333  using type_identity_t = typename type_identity<_Tp>::type;
3334 
3335 #define __cpp_lib_unwrap_ref 201811L
3336 
3337  /// Unwrap a reference_wrapper
3338  template<typename _Tp>
3339  struct unwrap_reference { using type = _Tp; };
3340 
3341  template<typename _Tp>
3342  struct unwrap_reference<reference_wrapper<_Tp>> { using type = _Tp&; };
3343 
3344  template<typename _Tp>
3345  using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
3346 
3347  /// Decay type and if it's a reference_wrapper, unwrap it
3348  template<typename _Tp>
3349  struct unwrap_ref_decay { using type = unwrap_reference_t<decay_t<_Tp>>; };
3350 
3351  template<typename _Tp>
3352  using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
3353 
3354 #define __cpp_lib_bounded_array_traits 201902L
3355 
3356  /// True for a type that is an array of known bound.
3357  template<typename _Tp>
3358  struct is_bounded_array
3359  : public __is_array_known_bounds<_Tp>
3360  { };
3361 
3362  /// True for a type that is an array of unknown bound.
3363  template<typename _Tp>
3364  struct is_unbounded_array
3365  : public __is_array_unknown_bounds<_Tp>
3366  { };
3367 
3368  /// @ingroup variable_templates
3369  template<typename _Tp>
3370  inline constexpr bool is_bounded_array_v
3371  = is_bounded_array<_Tp>::value;
3372 
3373  /// @ingroup variable_templates
3374  template<typename _Tp>
3375  inline constexpr bool is_unbounded_array_v
3376  = is_unbounded_array<_Tp>::value;
3377 
3378 #if __cplusplus > 202002L
3379 #define __cpp_lib_is_scoped_enum 202011L
3380 
3381  /// @since C++23
3382  //@{
3383 
3384  template<typename _Tp>
3385  struct is_scoped_enum
3386  : false_type
3387  { };
3388 
3389  template<typename _Tp>
3390  requires __is_enum(_Tp)
3391  && requires(_Tp __t) { __t = __t; } // fails if incomplete
3392  struct is_scoped_enum<_Tp>
3393  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3394  { };
3395 
3396  // FIXME remove this partial specialization and use remove_cv_t<_Tp> above
3397  // when PR c++/99968 is fixed.
3398  template<typename _Tp>
3399  requires __is_enum(_Tp)
3400  && requires(_Tp __t) { __t = __t; } // fails if incomplete
3401  struct is_scoped_enum<const _Tp>
3402  : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
3403  { };
3404 
3405  /**
3406  * @ingroup variable_templates
3407  */
3408  template<typename _Tp>
3409  inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
3410 #endif // C++23
3411 
3412 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
3413 
3414 #define __cpp_lib_is_constant_evaluated 201811L
3415 
3416  /// Returns true only when called during constant evaluation.
3417  constexpr inline bool
3418  is_constant_evaluated() noexcept
3419  { return __builtin_is_constant_evaluated(); }
3420  /// @}
3421 #endif
3422 
3423  /// @cond undocumented
3424  template<typename _From, typename _To>
3425  using __copy_cv = typename __match_cv_qualifiers<_From, _To>::__type;
3426 
3427  template<typename _Xp, typename _Yp>
3428  using __cond_res
3429  = decltype(false ? declval<_Xp(&)()>()() : declval<_Yp(&)()>()());
3430 
3431  template<typename _Ap, typename _Bp, typename = void>
3432  struct __common_ref_impl
3433  { };
3434 
3435  // [meta.trans.other], COMMON-REF(A, B)
3436  template<typename _Ap, typename _Bp>
3437  using __common_ref = typename __common_ref_impl<_Ap, _Bp>::type;
3438 
3439  // COND-RES(COPYCV(X, Y) &, COPYCV(Y, X) &)
3440  template<typename _Xp, typename _Yp>
3441  using __condres_cvref
3442  = __cond_res<__copy_cv<_Xp, _Yp>&, __copy_cv<_Yp, _Xp>&>;
3443 
3444  // If A and B are both lvalue reference types, ...
3445  template<typename _Xp, typename _Yp>
3446  struct __common_ref_impl<_Xp&, _Yp&, __void_t<__condres_cvref<_Xp, _Yp>>>
3447  : enable_if<is_reference_v<__condres_cvref<_Xp, _Yp>>,
3448  __condres_cvref<_Xp, _Yp>>
3449  { };
3450 
3451  // let C be remove_reference_t<COMMON-REF(X&, Y&)>&&
3452  template<typename _Xp, typename _Yp>
3453  using __common_ref_C = remove_reference_t<__common_ref<_Xp&, _Yp&>>&&;
3454 
3455  // If A and B are both rvalue reference types, ...
3456  template<typename _Xp, typename _Yp>
3457  struct __common_ref_impl<_Xp&&, _Yp&&,
3458  _Require<is_convertible<_Xp&&, __common_ref_C<_Xp, _Yp>>,
3459  is_convertible<_Yp&&, __common_ref_C<_Xp, _Yp>>>>
3460  { using type = __common_ref_C<_Xp, _Yp>; };
3461 
3462  // let D be COMMON-REF(const X&, Y&)
3463  template<typename _Xp, typename _Yp>
3464  using __common_ref_D = __common_ref<const _Xp&, _Yp&>;
3465 
3466  // If A is an rvalue reference and B is an lvalue reference, ...
3467  template<typename _Xp, typename _Yp>
3468  struct __common_ref_impl<_Xp&&, _Yp&,
3469  _Require<is_convertible<_Xp&&, __common_ref_D<_Xp, _Yp>>>>
3470  { using type = __common_ref_D<_Xp, _Yp>; };
3471 
3472  // If A is an lvalue reference and B is an rvalue reference, ...
3473  template<typename _Xp, typename _Yp>
3474  struct __common_ref_impl<_Xp&, _Yp&&>
3475  : __common_ref_impl<_Yp&&, _Xp&>
3476  { };
3477  /// @endcond
3478 
3479  template<typename _Tp, typename _Up,
3480  template<typename> class _TQual, template<typename> class _UQual>
3481  struct basic_common_reference
3482  { };
3483 
3484  /// @cond undocumented
3485  template<typename _Tp>
3486  struct __xref
3487  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>; };
3488 
3489  template<typename _Tp>
3490  struct __xref<_Tp&>
3491  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&; };
3492 
3493  template<typename _Tp>
3494  struct __xref<_Tp&&>
3495  { template<typename _Up> using __type = __copy_cv<_Tp, _Up>&&; };
3496 
3497  template<typename _Tp1, typename _Tp2>
3498  using __basic_common_ref
3499  = typename basic_common_reference<remove_cvref_t<_Tp1>,
3500  remove_cvref_t<_Tp2>,
3501  __xref<_Tp1>::template __type,
3502  __xref<_Tp2>::template __type>::type;
3503  /// @endcond
3504 
3505  template<typename... _Tp>
3506  struct common_reference;
3507 
3508  template<typename... _Tp>
3509  using common_reference_t = typename common_reference<_Tp...>::type;
3510 
3511  // If sizeof...(T) is zero, there shall be no member type.
3512  template<>
3513  struct common_reference<>
3514  { };
3515 
3516  // If sizeof...(T) is one ...
3517  template<typename _Tp0>
3518  struct common_reference<_Tp0>
3519  { using type = _Tp0; };
3520 
3521  /// @cond undocumented
3522  template<typename _Tp1, typename _Tp2, int _Bullet = 1, typename = void>
3523  struct __common_reference_impl
3524  : __common_reference_impl<_Tp1, _Tp2, _Bullet + 1>
3525  { };
3526 
3527  // If sizeof...(T) is two ...
3528  template<typename _Tp1, typename _Tp2>
3529  struct common_reference<_Tp1, _Tp2>
3530  : __common_reference_impl<_Tp1, _Tp2>
3531  { };
3532 
3533  // If T1 and T2 are reference types and COMMON-REF(T1, T2) is well-formed, ...
3534  template<typename _Tp1, typename _Tp2>
3535  struct __common_reference_impl<_Tp1&, _Tp2&, 1,
3536  void_t<__common_ref<_Tp1&, _Tp2&>>>
3537  { using type = __common_ref<_Tp1&, _Tp2&>; };
3538 
3539  template<typename _Tp1, typename _Tp2>
3540  struct __common_reference_impl<_Tp1&&, _Tp2&&, 1,
3541  void_t<__common_ref<_Tp1&&, _Tp2&&>>>
3542  { using type = __common_ref<_Tp1&&, _Tp2&&>; };
3543 
3544  template<typename _Tp1, typename _Tp2>
3545  struct __common_reference_impl<_Tp1&, _Tp2&&, 1,
3546  void_t<__common_ref<_Tp1&, _Tp2&&>>>
3547  { using type = __common_ref<_Tp1&, _Tp2&&>; };
3548 
3549  template<typename _Tp1, typename _Tp2>
3550  struct __common_reference_impl<_Tp1&&, _Tp2&, 1,
3551  void_t<__common_ref<_Tp1&&, _Tp2&>>>
3552  { using type = __common_ref<_Tp1&&, _Tp2&>; };
3553 
3554  // Otherwise, if basic_common_reference<...>::type is well-formed, ...
3555  template<typename _Tp1, typename _Tp2>
3556  struct __common_reference_impl<_Tp1, _Tp2, 2,
3557  void_t<__basic_common_ref<_Tp1, _Tp2>>>
3558  { using type = __basic_common_ref<_Tp1, _Tp2>; };
3559 
3560  // Otherwise, if COND-RES(T1, T2) is well-formed, ...
3561  template<typename _Tp1, typename _Tp2>
3562  struct __common_reference_impl<_Tp1, _Tp2, 3,
3563  void_t<__cond_res<_Tp1, _Tp2>>>
3564  { using type = __cond_res<_Tp1, _Tp2>; };
3565 
3566  // Otherwise, if common_type_t<T1, T2> is well-formed, ...
3567  template<typename _Tp1, typename _Tp2>
3568  struct __common_reference_impl<_Tp1, _Tp2, 4,
3569  void_t<common_type_t<_Tp1, _Tp2>>>
3570  { using type = common_type_t<_Tp1, _Tp2>; };
3571 
3572  // Otherwise, there shall be no member type.
3573  template<typename _Tp1, typename _Tp2>
3574  struct __common_reference_impl<_Tp1, _Tp2, 5, void>
3575  { };
3576 
3577  // Otherwise, if sizeof...(T) is greater than two, ...
3578  template<typename _Tp1, typename _Tp2, typename... _Rest>
3579  struct common_reference<_Tp1, _Tp2, _Rest...>
3580  : __common_type_fold<common_reference<_Tp1, _Tp2>,
3581  __common_type_pack<_Rest...>>
3582  { };
3583 
3584  // Reuse __common_type_fold for common_reference<T1, T2, Rest...>
3585  template<typename _Tp1, typename _Tp2, typename... _Rest>
3586  struct __common_type_fold<common_reference<_Tp1, _Tp2>,
3587  __common_type_pack<_Rest...>,
3588  void_t<common_reference_t<_Tp1, _Tp2>>>
3589  : public common_reference<common_reference_t<_Tp1, _Tp2>, _Rest...>
3590  { };
3591  /// @endcond
3592 
3593 #endif // C++2a
3594 
3595  /// @} group metaprogramming
3596 
3597 _GLIBCXX_END_NAMESPACE_VERSION
3598 } // namespace std
3599 
3600 #endif // C++11
3601 
3602 #endif // _GLIBCXX_TYPE_TRAITS
typename remove_reference< _Tp >::type remove_reference_t
Alias template for remove_reference.
Definition: type_traits:1645
typename result_of< _Tp >::type result_of_t
Alias template for result_of.
Definition: type_traits:2601
constexpr bool is_nothrow_swappable_v
is_nothrow_swappable_v
Definition: type_traits:2775
typename add_rvalue_reference< _Tp >::type add_rvalue_reference_t
Alias template for add_rvalue_reference.
Definition: type_traits:1653
integral_constant< bool, __v > bool_constant
Alias template for compile-time boolean constant types.
Definition: type_traits:99
typename make_unsigned< _Tp >::type make_unsigned_t
Alias template for make_unsigned.
Definition: type_traits:1980
void void_t
A metafunction that always yields void, used for detecting valid types.
Definition: type_traits:2607
constexpr bool is_swappable_v
is_swappable_v
Definition: type_traits:2770
typename aligned_storage< _Len, _Align >::type aligned_storage_t
Alias template for aligned_storage.
Definition: type_traits:2574
integral_constant< bool, true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:83
typename remove_cv< _Tp >::type remove_cv_t
Alias template for remove_cv.
Definition: type_traits:1584
typename remove_all_extents< _Tp >::type remove_all_extents_t
Alias template for remove_all_extents.
Definition: type_traits:2018
typename common_type< _Tp... >::type common_type_t
Alias template for common_type.
Definition: type_traits:2593
typename conditional< _Cond, _Iftrue, _Iffalse >::type conditional_t
Alias template for conditional.
Definition: type_traits:2589
typename add_const< _Tp >::type add_const_t
Alias template for add_const.
Definition: type_traits:1588
typename remove_pointer< _Tp >::type remove_pointer_t
Alias template for remove_pointer.
Definition: type_traits:2055
typename add_cv< _Tp >::type add_cv_t
Alias template for add_cv.
Definition: type_traits:1596
integral_constant< bool, false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:86
typename remove_const< _Tp >::type remove_const_t
Alias template for remove_const.
Definition: type_traits:1576
constexpr bool is_swappable_with_v
is_swappable_with_v
Definition: type_traits:2866
typename add_volatile< _Tp >::type add_volatile_t
Alias template for add_volatile.
Definition: type_traits:1592
typename remove_volatile< _Tp >::type remove_volatile_t
Alias template for remove_volatile.
Definition: type_traits:1580
typename add_lvalue_reference< _Tp >::type add_lvalue_reference_t
Alias template for add_lvalue_reference.
Definition: type_traits:1649
typename add_pointer< _Tp >::type add_pointer_t
Alias template for add_pointer.
Definition: type_traits:2059
typename remove_extent< _Tp >::type remove_extent_t
Alias template for remove_extent.
Definition: type_traits:2014
typename underlying_type< _Tp >::type underlying_type_t
Alias template for underlying_type.
Definition: type_traits:2597
typename decay< _Tp >::type decay_t
Alias template for decay.
Definition: type_traits:2581
typename make_signed< _Tp >::type make_signed_t
Alias template for make_signed.
Definition: type_traits:1976
typename enable_if< _Cond, _Tp >::type enable_if_t
Alias template for enable_if.
Definition: type_traits:2585
typename invoke_result< _Fn, _Args... >::type invoke_result_t
std::invoke_result_t
Definition: type_traits:3009
constexpr bool is_nothrow_swappable_with_v
is_nothrow_swappable_with_v
Definition: type_traits:2871
auto declval() noexcept -> decltype(__declval< _Tp >(0))
Definition: type_traits:2364
void swap(any &__x, any &__y) noexcept
Exchange the states of two any objects.
Definition: any:422
ISO C++ entities toplevel namespace is std.
integral_constant
Definition: type_traits:66
Define a member typedef type to one of two argument types.
Definition: type_traits:2227
is_reference
Definition: type_traits:560
is_function
Definition: type_traits:520
is_void
Definition: type_traits:272
remove_cv
Definition: type_traits:1538
is_const
Definition: type_traits:684
is_integral
Definition: type_traits:394
is_floating_point
Definition: type_traits:424
is_array
Definition: type_traits:429
is_pointer
Definition: type_traits:451
is_lvalue_reference
Definition: type_traits:456
is_rvalue_reference
Definition: type_traits:465
is_member_object_pointer
Definition: type_traits:483
is_member_function_pointer
Definition: type_traits:497
is_enum
Definition: type_traits:503
is_union
Definition: type_traits:509
is_class
Definition: type_traits:515
is_null_pointer (LWG 2247).
Definition: type_traits:544
__is_nullptr_t (deprecated extension).
Definition: type_traits:551
is_arithmetic
Definition: type_traits:566
is_fundamental
Definition: type_traits:573
is_object
Definition: type_traits:580
is_member_pointer
Definition: type_traits:611
is_scalar
Definition: type_traits:590
is_compound
Definition: type_traits:595
is_same
Definition: type_traits:1410
is_volatile
Definition: type_traits:693
is_trivial
Definition: type_traits:703
is_trivially_copyable
Definition: type_traits:712
is_standard_layout
Definition: type_traits:721
is_empty
Definition: type_traits:757
is_polymorphic
Definition: type_traits:763
is_final
Definition: type_traits:772
is_abstract
Definition: type_traits:779
is_signed
Definition: type_traits:797
is_unsigned
Definition: type_traits:803
extent
Definition: type_traits:1383
remove_all_extents
Definition: type_traits:2001
is_destructible
Definition: type_traits:884
is_nothrow_destructible
Definition: type_traits:938
is_constructible
Definition: type_traits:954
is_default_constructible
Definition: type_traits:963
is_copy_constructible
Definition: type_traits:986
is_move_constructible
Definition: type_traits:1009
is_nothrow_constructible
Definition: type_traits:1024
is_nothrow_default_constructible
Definition: type_traits:1033
is_nothrow_copy_constructible
Definition: type_traits:1056
is_nothrow_move_constructible
Definition: type_traits:1079
is_assignable
Definition: type_traits:1088
is_copy_assignable
Definition: type_traits:1109
is_move_assignable
Definition: type_traits:1130
is_nothrow_assignable
Definition: type_traits:1143
is_nothrow_copy_assignable
Definition: type_traits:1164
is_nothrow_move_assignable
Definition: type_traits:1185
is_trivially_constructible
Definition: type_traits:1194
is_trivially_default_constructible
Definition: type_traits:1203
is_trivially_copy_constructible
Definition: type_traits:1256
is_trivially_move_constructible
Definition: type_traits:1279
is_trivially_assignable
Definition: type_traits:1288
is_trivially_copy_assignable
Definition: type_traits:1309
is_trivially_move_assignable
Definition: type_traits:1330
is_trivially_destructible
Definition: type_traits:1340
has_virtual_destructor
Definition: type_traits:1350
alignment_of
Definition: type_traits:1362
is_base_of
Definition: type_traits:1423
is_convertible
Definition: type_traits:1459
remove_const
Definition: type_traits:1520
remove_volatile
Definition: type_traits:1529
add_const
Definition: type_traits:1555
add_volatile
Definition: type_traits:1560
add_cv
Definition: type_traits:1565
remove_reference
Definition: type_traits:1604
add_lvalue_reference
Definition: type_traits:1626
add_rvalue_reference
Definition: type_traits:1640
make_unsigned
Definition: type_traits:1839
make_signed
Definition: type_traits:1967
remove_extent
Definition: type_traits:1988
remove_pointer
Definition: type_traits:2035
add_pointer
Definition: type_traits:2050
Alignment type.
Definition: type_traits:2085
Provide aligned storage for types.
Definition: type_traits:2123
aligned_storage< _S_len, alignment_value >::type type
The storage.
Definition: type_traits:2134
Define a member typedef type only if a boolean constant is true.
Definition: type_traits:2200
common_type
Definition: type_traits:2236
The underlying type of an enum.
Definition: type_traits:2349
result_of
Definition: type_traits:2373
Metafunctions used for detecting swappable types: p0185r1.
Definition: type_traits:2753
is_nothrow_swappable
Definition: type_traits:2762
is_swappable_with
Definition: type_traits:2845
is_nothrow_swappable_with
Definition: type_traits:2856
std::invoke_result
Definition: type_traits:2999
std::is_invocable
Definition: type_traits:3015
std::is_invocable_r
Definition: type_traits:3027
std::is_nothrow_invocable
Definition: type_traits:3042
std::is_nothrow_invocable_r
Definition: type_traits:3067