libstdc++
bits/alloc_traits.h
Go to the documentation of this file.
1 // Allocator traits -*- C++ -*-
2 
3 // Copyright (C) 2011-2024 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file bits/alloc_traits.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{memory}
28  */
29 
30 #ifndef _ALLOC_TRAITS_H
31 #define _ALLOC_TRAITS_H 1
32 
33 #include <bits/stl_construct.h>
34 #include <bits/memoryfwd.h>
35 #if __cplusplus >= 201103L
36 # include <bits/ptr_traits.h>
37 # include <ext/numeric_traits.h>
38 # if _GLIBCXX_HOSTED
39 # include <bits/allocator.h>
40 # endif
41 # if __cpp_exceptions
42 # include <bits/stl_iterator.h> // __make_move_if_noexcept_iterator
43 # endif
44 #endif
45 
46 namespace std _GLIBCXX_VISIBILITY(default)
47 {
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
49 
50 #if __cplusplus >= 201103L
51  /// @cond undocumented
52  struct __allocator_traits_base
53  {
54  template<typename _Tp, typename _Up, typename = void>
55  struct __rebind : __replace_first_arg<_Tp, _Up>
56  {
57  static_assert(is_same<
58  typename __replace_first_arg<_Tp, typename _Tp::value_type>::type,
59  _Tp>::value,
60  "allocator_traits<A>::rebind_alloc<A::value_type> must be A");
61  };
62 
63  template<typename _Tp, typename _Up>
64  struct __rebind<_Tp, _Up,
65  __void_t<typename _Tp::template rebind<_Up>::other>>
66  {
67  using type = typename _Tp::template rebind<_Up>::other;
68 
69  static_assert(is_same<
70  typename _Tp::template rebind<typename _Tp::value_type>::other,
71  _Tp>::value,
72  "allocator_traits<A>::rebind_alloc<A::value_type> must be A");
73  };
74 
75  protected:
76  template<typename _Tp>
77  using __pointer = typename _Tp::pointer;
78  template<typename _Tp>
79  using __c_pointer = typename _Tp::const_pointer;
80  template<typename _Tp>
81  using __v_pointer = typename _Tp::void_pointer;
82  template<typename _Tp>
83  using __cv_pointer = typename _Tp::const_void_pointer;
84  template<typename _Tp>
85  using __pocca = typename _Tp::propagate_on_container_copy_assignment;
86  template<typename _Tp>
87  using __pocma = typename _Tp::propagate_on_container_move_assignment;
88  template<typename _Tp>
89  using __pocs = typename _Tp::propagate_on_container_swap;
90  template<typename _Tp>
91  using __equal = __type_identity<typename _Tp::is_always_equal>;
92  };
93 
94  template<typename _Alloc, typename _Up>
95  using __alloc_rebind
96  = typename __allocator_traits_base::template __rebind<_Alloc, _Up>::type;
97  /// @endcond
98 
99  /**
100  * @brief Uniform interface to all allocator types.
101  * @headerfile memory
102  * @ingroup allocators
103  * @since C++11
104  */
105  template<typename _Alloc>
106  struct allocator_traits : __allocator_traits_base
107  {
108  /// The allocator type
109  typedef _Alloc allocator_type;
110  /// The allocated type
111  typedef typename _Alloc::value_type value_type;
112 
113  /**
114  * @brief The allocator's pointer type.
115  *
116  * @c Alloc::pointer if that type exists, otherwise @c value_type*
117  */
118  using pointer = __detected_or_t<value_type*, __pointer, _Alloc>;
119 
120  private:
121  // Select _Func<_Alloc> or pointer_traits<pointer>::rebind<_Tp>
122  template<template<typename> class _Func, typename _Tp, typename = void>
123  struct _Ptr
124  {
125  using type = typename pointer_traits<pointer>::template rebind<_Tp>;
126  };
127 
128  template<template<typename> class _Func, typename _Tp>
129  struct _Ptr<_Func, _Tp, __void_t<_Func<_Alloc>>>
130  {
131  using type = _Func<_Alloc>;
132  };
133 
134  // Select _A2::difference_type or pointer_traits<_Ptr>::difference_type
135  template<typename _A2, typename _PtrT, typename = void>
136  struct _Diff
137  { using type = typename pointer_traits<_PtrT>::difference_type; };
138 
139  template<typename _A2, typename _PtrT>
140  struct _Diff<_A2, _PtrT, __void_t<typename _A2::difference_type>>
141  { using type = typename _A2::difference_type; };
142 
143  // Select _A2::size_type or make_unsigned<_DiffT>::type
144  template<typename _A2, typename _DiffT, typename = void>
145  struct _Size : make_unsigned<_DiffT> { };
146 
147  template<typename _A2, typename _DiffT>
148  struct _Size<_A2, _DiffT, __void_t<typename _A2::size_type>>
149  { using type = typename _A2::size_type; };
150 
151  public:
152  /**
153  * @brief The allocator's const pointer type.
154  *
155  * @c Alloc::const_pointer if that type exists, otherwise
156  * <tt> pointer_traits<pointer>::rebind<const value_type> </tt>
157  */
158  using const_pointer = typename _Ptr<__c_pointer, const value_type>::type;
159 
160  /**
161  * @brief The allocator's void pointer type.
162  *
163  * @c Alloc::void_pointer if that type exists, otherwise
164  * <tt> pointer_traits<pointer>::rebind<void> </tt>
165  */
166  using void_pointer = typename _Ptr<__v_pointer, void>::type;
167 
168  /**
169  * @brief The allocator's const void pointer type.
170  *
171  * @c Alloc::const_void_pointer if that type exists, otherwise
172  * <tt> pointer_traits<pointer>::rebind<const void> </tt>
173  */
174  using const_void_pointer = typename _Ptr<__cv_pointer, const void>::type;
175 
176  /**
177  * @brief The allocator's difference type
178  *
179  * @c Alloc::difference_type if that type exists, otherwise
180  * <tt> pointer_traits<pointer>::difference_type </tt>
181  */
182  using difference_type = typename _Diff<_Alloc, pointer>::type;
183 
184  /**
185  * @brief The allocator's size type
186  *
187  * @c Alloc::size_type if that type exists, otherwise
188  * <tt> make_unsigned<difference_type>::type </tt>
189  */
190  using size_type = typename _Size<_Alloc, difference_type>::type;
191 
192  /**
193  * @brief How the allocator is propagated on copy assignment
194  *
195  * @c Alloc::propagate_on_container_copy_assignment if that type exists,
196  * otherwise @c false_type
197  */
199  = __detected_or_t<false_type, __pocca, _Alloc>;
200 
201  /**
202  * @brief How the allocator is propagated on move assignment
203  *
204  * @c Alloc::propagate_on_container_move_assignment if that type exists,
205  * otherwise @c false_type
206  */
208  = __detected_or_t<false_type, __pocma, _Alloc>;
209 
210  /**
211  * @brief How the allocator is propagated on swap
212  *
213  * @c Alloc::propagate_on_container_swap if that type exists,
214  * otherwise @c false_type
215  */
217  = __detected_or_t<false_type, __pocs, _Alloc>;
218 
219  /**
220  * @brief Whether all instances of the allocator type compare equal.
221  *
222  * @c Alloc::is_always_equal if that type exists,
223  * otherwise @c is_empty<Alloc>::type
224  */
226  = typename __detected_or_t<is_empty<_Alloc>, __equal, _Alloc>::type;
227 
228  template<typename _Tp>
229  using rebind_alloc = __alloc_rebind<_Alloc, _Tp>;
230  template<typename _Tp>
232 
233  private:
234  template<typename _Alloc2>
235  static constexpr auto
236  _S_allocate(_Alloc2& __a, size_type __n, const_void_pointer __hint, int)
237  -> decltype(__a.allocate(__n, __hint))
238  { return __a.allocate(__n, __hint); }
239 
240  template<typename _Alloc2>
241  static constexpr pointer
242  _S_allocate(_Alloc2& __a, size_type __n, const_void_pointer, ...)
243  { return __a.allocate(__n); }
244 
245  template<typename _Tp, typename... _Args>
246  struct __construct_helper
247  {
248  template<typename _Alloc2,
249  typename = decltype(std::declval<_Alloc2*>()->construct(
250  std::declval<_Tp*>(), std::declval<_Args>()...))>
251  static true_type __test(int);
252 
253  template<typename>
254  static false_type __test(...);
255 
256  using type = decltype(__test<_Alloc>(0));
257  };
258 
259  template<typename _Tp, typename... _Args>
260  using __has_construct
261  = typename __construct_helper<_Tp, _Args...>::type;
262 
263  template<typename _Tp, typename... _Args>
264  static _GLIBCXX14_CONSTEXPR _Require<__has_construct<_Tp, _Args...>>
265  _S_construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
266  noexcept(noexcept(__a.construct(__p, std::forward<_Args>(__args)...)))
267  { __a.construct(__p, std::forward<_Args>(__args)...); }
268 
269  template<typename _Tp, typename... _Args>
270  static _GLIBCXX14_CONSTEXPR
271  _Require<__and_<__not_<__has_construct<_Tp, _Args...>>,
272  is_constructible<_Tp, _Args...>>>
273  _S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
275  {
276 #if __cplusplus <= 201703L
277  ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
278 #else
279  std::construct_at(__p, std::forward<_Args>(__args)...);
280 #endif
281  }
282 
283  template<typename _Alloc2, typename _Tp>
284  static _GLIBCXX14_CONSTEXPR auto
285  _S_destroy(_Alloc2& __a, _Tp* __p, int)
286  noexcept(noexcept(__a.destroy(__p)))
287  -> decltype(__a.destroy(__p))
288  { __a.destroy(__p); }
289 
290  template<typename _Alloc2, typename _Tp>
291  static _GLIBCXX14_CONSTEXPR void
292  _S_destroy(_Alloc2&, _Tp* __p, ...)
293  noexcept(std::is_nothrow_destructible<_Tp>::value)
294  { std::_Destroy(__p); }
295 
296  template<typename _Alloc2>
297  static constexpr auto
298  _S_max_size(_Alloc2& __a, int)
299  -> decltype(__a.max_size())
300  { return __a.max_size(); }
301 
302  template<typename _Alloc2>
303  static constexpr size_type
304  _S_max_size(_Alloc2&, ...)
305  {
306  // _GLIBCXX_RESOLVE_LIB_DEFECTS
307  // 2466. allocator_traits::max_size() default behavior is incorrect
308  return __gnu_cxx::__numeric_traits<size_type>::__max
309  / sizeof(value_type);
310  }
311 
312  template<typename _Alloc2>
313  static constexpr auto
314  _S_select(_Alloc2& __a, int)
315  -> decltype(__a.select_on_container_copy_construction())
316  { return __a.select_on_container_copy_construction(); }
317 
318  template<typename _Alloc2>
319  static constexpr _Alloc2
320  _S_select(_Alloc2& __a, ...)
321  { return __a; }
322 
323  public:
324 
325  /**
326  * @brief Allocate memory.
327  * @param __a An allocator.
328  * @param __n The number of objects to allocate space for.
329  *
330  * Calls @c a.allocate(n)
331  */
332  _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
333  allocate(_Alloc& __a, size_type __n)
334  { return __a.allocate(__n); }
335 
336  /**
337  * @brief Allocate memory.
338  * @param __a An allocator.
339  * @param __n The number of objects to allocate space for.
340  * @param __hint Aid to locality.
341  * @return Memory of suitable size and alignment for @a n objects
342  * of type @c value_type
343  *
344  * Returns <tt> a.allocate(n, hint) </tt> if that expression is
345  * well-formed, otherwise returns @c a.allocate(n)
346  */
347  _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
348  allocate(_Alloc& __a, size_type __n, const_void_pointer __hint)
349  { return _S_allocate(__a, __n, __hint, 0); }
350 
351  /**
352  * @brief Deallocate memory.
353  * @param __a An allocator.
354  * @param __p Pointer to the memory to deallocate.
355  * @param __n The number of objects space was allocated for.
356  *
357  * Calls <tt> a.deallocate(p, n) </tt>
358  */
359  static _GLIBCXX20_CONSTEXPR void
360  deallocate(_Alloc& __a, pointer __p, size_type __n)
361  { __a.deallocate(__p, __n); }
362 
363  /**
364  * @brief Construct an object of type `_Tp`
365  * @param __a An allocator.
366  * @param __p Pointer to memory of suitable size and alignment for Tp
367  * @param __args Constructor arguments.
368  *
369  * Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
370  * if that expression is well-formed, otherwise uses placement-new
371  * to construct an object of type @a _Tp at location @a __p from the
372  * arguments @a __args...
373  */
374  template<typename _Tp, typename... _Args>
375  static _GLIBCXX20_CONSTEXPR auto
376  construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
377  noexcept(noexcept(_S_construct(__a, __p,
378  std::forward<_Args>(__args)...)))
379  -> decltype(_S_construct(__a, __p, std::forward<_Args>(__args)...))
380  { _S_construct(__a, __p, std::forward<_Args>(__args)...); }
381 
382  /**
383  * @brief Destroy an object of type @a _Tp
384  * @param __a An allocator.
385  * @param __p Pointer to the object to destroy
386  *
387  * Calls @c __a.destroy(__p) if that expression is well-formed,
388  * otherwise calls @c __p->~_Tp()
389  */
390  template<typename _Tp>
391  static _GLIBCXX20_CONSTEXPR void
392  destroy(_Alloc& __a, _Tp* __p)
393  noexcept(noexcept(_S_destroy(__a, __p, 0)))
394  { _S_destroy(__a, __p, 0); }
395 
396  /**
397  * @brief The maximum supported allocation size
398  * @param __a An allocator.
399  * @return @c __a.max_size() or @c numeric_limits<size_type>::max()
400  *
401  * Returns @c __a.max_size() if that expression is well-formed,
402  * otherwise returns @c numeric_limits<size_type>::max()
403  */
404  static _GLIBCXX20_CONSTEXPR size_type
405  max_size(const _Alloc& __a) noexcept
406  { return _S_max_size(__a, 0); }
407 
408  /**
409  * @brief Obtain an allocator to use when copying a container.
410  * @param __rhs An allocator.
411  * @return @c __rhs.select_on_container_copy_construction() or @a __rhs
412  *
413  * Returns @c __rhs.select_on_container_copy_construction() if that
414  * expression is well-formed, otherwise returns @a __rhs
415  */
416  static _GLIBCXX20_CONSTEXPR _Alloc
418  { return _S_select(__rhs, 0); }
419  };
420 
421 #if _GLIBCXX_HOSTED
422  /// Partial specialization for std::allocator.
423  template<typename _Tp>
425  {
426  /// The allocator type
428 
429  /// The allocated type
430  using value_type = _Tp;
431 
432  /// The allocator's pointer type.
433  using pointer = _Tp*;
434 
435  /// The allocator's const pointer type.
436  using const_pointer = const _Tp*;
437 
438  /// The allocator's void pointer type.
439  using void_pointer = void*;
440 
441  /// The allocator's const void pointer type.
442  using const_void_pointer = const void*;
443 
444  /// The allocator's difference type
445  using difference_type = std::ptrdiff_t;
446 
447  /// The allocator's size type
448  using size_type = std::size_t;
449 
450  /// How the allocator is propagated on copy assignment
452 
453  /// How the allocator is propagated on move assignment
455 
456  /// How the allocator is propagated on swap
458 
459  /// Whether all instances of the allocator type compare equal.
461 
462  template<typename _Up>
464 
465  template<typename _Up>
467 
468  /**
469  * @brief Allocate memory.
470  * @param __a An allocator.
471  * @param __n The number of objects to allocate space for.
472  *
473  * Calls @c a.allocate(n)
474  */
475  [[__nodiscard__,__gnu__::__always_inline__]]
476  static _GLIBCXX20_CONSTEXPR pointer
478  { return __a.allocate(__n); }
479 
480  /**
481  * @brief Allocate memory.
482  * @param __a An allocator.
483  * @param __n The number of objects to allocate space for.
484  * @param __hint Aid to locality.
485  * @return Memory of suitable size and alignment for @a n objects
486  * of type @c value_type
487  *
488  * Returns <tt> a.allocate(n, hint) </tt>
489  */
490  [[__nodiscard__,__gnu__::__always_inline__]]
491  static _GLIBCXX20_CONSTEXPR pointer
493  [[maybe_unused]] const_void_pointer __hint)
494  {
495 #if __cplusplus <= 201703L
496  return __a.allocate(__n, __hint);
497 #else
498  return __a.allocate(__n);
499 #endif
500  }
501 
502  /**
503  * @brief Deallocate memory.
504  * @param __a An allocator.
505  * @param __p Pointer to the memory to deallocate.
506  * @param __n The number of objects space was allocated for.
507  *
508  * Calls <tt> a.deallocate(p, n) </tt>
509  */
510  [[__gnu__::__always_inline__]]
511  static _GLIBCXX20_CONSTEXPR void
513  { __a.deallocate(__p, __n); }
514 
515  /**
516  * @brief Construct an object of type `_Up`
517  * @param __a An allocator.
518  * @param __p Pointer to memory of suitable size and alignment for
519  * an object of type `_Up`.
520  * @param __args Constructor arguments.
521  *
522  * Calls `__a.construct(__p, std::forward<_Args>(__args)...)`
523  * in C++11, C++14 and C++17. Changed in C++20 to call
524  * `std::construct_at(__p, std::forward<_Args>(__args)...)` instead.
525  */
526  template<typename _Up, typename... _Args>
527  [[__gnu__::__always_inline__]]
528  static _GLIBCXX20_CONSTEXPR void
529  construct(allocator_type& __a __attribute__((__unused__)), _Up* __p,
530  _Args&&... __args)
532  {
533 #if __cplusplus <= 201703L
534  __a.construct(__p, std::forward<_Args>(__args)...);
535 #else
536  std::construct_at(__p, std::forward<_Args>(__args)...);
537 #endif
538  }
539 
540  /**
541  * @brief Destroy an object of type @a _Up
542  * @param __a An allocator.
543  * @param __p Pointer to the object to destroy
544  *
545  * Calls @c __a.destroy(__p).
546  */
547  template<typename _Up>
548  [[__gnu__::__always_inline__]]
549  static _GLIBCXX20_CONSTEXPR void
550  destroy(allocator_type& __a __attribute__((__unused__)), _Up* __p)
552  {
553 #if __cplusplus <= 201703L
554  __a.destroy(__p);
555 #else
556  std::destroy_at(__p);
557 #endif
558  }
559 
560  /**
561  * @brief The maximum supported allocation size
562  * @param __a An allocator.
563  * @return @c __a.max_size()
564  */
565  [[__gnu__::__always_inline__]]
566  static _GLIBCXX20_CONSTEXPR size_type
567  max_size(const allocator_type& __a __attribute__((__unused__))) noexcept
568  {
569 #if __cplusplus <= 201703L
570  return __a.max_size();
571 #else
572  return size_t(-1) / sizeof(value_type);
573 #endif
574  }
575 
576  /**
577  * @brief Obtain an allocator to use when copying a container.
578  * @param __rhs An allocator.
579  * @return @c __rhs
580  */
581  [[__gnu__::__always_inline__]]
582  static _GLIBCXX20_CONSTEXPR allocator_type
584  { return __rhs; }
585  };
586 
587  /// Explicit specialization for std::allocator<void>.
588  template<>
590  {
591  /// The allocator type
593 
594  /// The allocated type
595  using value_type = void;
596 
597  /// The allocator's pointer type.
598  using pointer = void*;
599 
600  /// The allocator's const pointer type.
601  using const_pointer = const void*;
602 
603  /// The allocator's void pointer type.
604  using void_pointer = void*;
605 
606  /// The allocator's const void pointer type.
607  using const_void_pointer = const void*;
608 
609  /// The allocator's difference type
610  using difference_type = std::ptrdiff_t;
611 
612  /// The allocator's size type
613  using size_type = std::size_t;
614 
615  /// How the allocator is propagated on copy assignment
617 
618  /// How the allocator is propagated on move assignment
620 
621  /// How the allocator is propagated on swap
623 
624  /// Whether all instances of the allocator type compare equal.
626 
627  template<typename _Up>
629 
630  template<typename _Up>
632 
633  /// allocate is ill-formed for allocator<void>
634  static void*
635  allocate(allocator_type&, size_type, const void* = nullptr) = delete;
636 
637  /// deallocate is ill-formed for allocator<void>
638  static void
639  deallocate(allocator_type&, void*, size_type) = delete;
640 
641  /**
642  * @brief Construct an object of type `_Up`
643  * @param __a An allocator.
644  * @param __p Pointer to memory of suitable size and alignment for
645  * an object of type `_Up`.
646  * @param __args Constructor arguments.
647  *
648  * Calls `__a.construct(__p, std::forward<_Args>(__args)...)`
649  * in C++11, C++14 and C++17. Changed in C++20 to call
650  * `std::construct_at(__p, std::forward<_Args>(__args)...)` instead.
651  */
652  template<typename _Up, typename... _Args>
653  [[__gnu__::__always_inline__]]
654  static _GLIBCXX20_CONSTEXPR void
655  construct(allocator_type&, _Up* __p, _Args&&... __args)
657  { std::_Construct(__p, std::forward<_Args>(__args)...); }
658 
659  /**
660  * @brief Destroy an object of type `_Up`
661  * @param __a An allocator.
662  * @param __p Pointer to the object to destroy
663  *
664  * Invokes the destructor for `*__p`.
665  */
666  template<typename _Up>
667  [[__gnu__::__always_inline__]]
668  static _GLIBCXX20_CONSTEXPR void
671  { std::_Destroy(__p); }
672 
673  /// max_size is ill-formed for allocator<void>
674  static size_type
675  max_size(const allocator_type&) = delete;
676 
677  /**
678  * @brief Obtain an allocator to use when copying a container.
679  * @param __rhs An allocator.
680  * @return `__rhs`
681  */
682  [[__gnu__::__always_inline__]]
683  static _GLIBCXX20_CONSTEXPR allocator_type
685  { return __rhs; }
686  };
687 #endif
688 
689  /// @cond undocumented
690 #if __cplusplus < 201703L
691  template<typename _Alloc>
692  [[__gnu__::__always_inline__]]
693  inline void
694  __do_alloc_on_copy(_Alloc& __one, const _Alloc& __two, true_type)
695  { __one = __two; }
696 
697  template<typename _Alloc>
698  [[__gnu__::__always_inline__]]
699  inline void
700  __do_alloc_on_copy(_Alloc&, const _Alloc&, false_type)
701  { }
702 #endif
703 
704  template<typename _Alloc>
705  [[__gnu__::__always_inline__]]
706  _GLIBCXX14_CONSTEXPR inline void
707  __alloc_on_copy(_Alloc& __one, const _Alloc& __two)
708  {
709  using __traits = allocator_traits<_Alloc>;
710  using __pocca =
711  typename __traits::propagate_on_container_copy_assignment::type;
712 #if __cplusplus >= 201703L
713  if constexpr (__pocca::value)
714  __one = __two;
715 #else
716  __do_alloc_on_copy(__one, __two, __pocca());
717 #endif
718  }
719 
720  template<typename _Alloc>
721  [[__gnu__::__always_inline__]]
722  constexpr _Alloc
723  __alloc_on_copy(const _Alloc& __a)
724  {
725  typedef allocator_traits<_Alloc> __traits;
726  return __traits::select_on_container_copy_construction(__a);
727  }
728 
729 #if __cplusplus < 201703L
730  template<typename _Alloc>
731  [[__gnu__::__always_inline__]]
732  inline void __do_alloc_on_move(_Alloc& __one, _Alloc& __two, true_type)
733  { __one = std::move(__two); }
734 
735  template<typename _Alloc>
736  [[__gnu__::__always_inline__]]
737  inline void __do_alloc_on_move(_Alloc&, _Alloc&, false_type)
738  { }
739 #endif
740 
741  template<typename _Alloc>
742  [[__gnu__::__always_inline__]]
743  _GLIBCXX14_CONSTEXPR inline void
744  __alloc_on_move(_Alloc& __one, _Alloc& __two)
745  {
746  using __traits = allocator_traits<_Alloc>;
747  using __pocma
748  = typename __traits::propagate_on_container_move_assignment::type;
749 #if __cplusplus >= 201703L
750  if constexpr (__pocma::value)
751  __one = std::move(__two);
752 #else
753  __do_alloc_on_move(__one, __two, __pocma());
754 #endif
755  }
756 
757 #if __cplusplus < 201703L
758  template<typename _Alloc>
759  [[__gnu__::__always_inline__]]
760  inline void __do_alloc_on_swap(_Alloc& __one, _Alloc& __two, true_type)
761  {
762  using std::swap;
763  swap(__one, __two);
764  }
765 
766  template<typename _Alloc>
767  [[__gnu__::__always_inline__]]
768  inline void __do_alloc_on_swap(_Alloc&, _Alloc&, false_type)
769  { }
770 #endif
771 
772  template<typename _Alloc>
773  [[__gnu__::__always_inline__]]
774  _GLIBCXX14_CONSTEXPR inline void
775  __alloc_on_swap(_Alloc& __one, _Alloc& __two)
776  {
777  using __traits = allocator_traits<_Alloc>;
778  using __pocs = typename __traits::propagate_on_container_swap::type;
779 #if __cplusplus >= 201703L
780  if constexpr (__pocs::value)
781  {
782  using std::swap;
783  swap(__one, __two);
784  }
785 #else
786  __do_alloc_on_swap(__one, __two, __pocs());
787 #endif
788  }
789 
790  template<typename _Alloc, typename _Tp,
791  typename _ValueT = __remove_cvref_t<typename _Alloc::value_type>,
792  typename = void>
793  struct __is_alloc_insertable_impl
794  : false_type
795  { };
796 
797  template<typename _Alloc, typename _Tp, typename _ValueT>
798  struct __is_alloc_insertable_impl<_Alloc, _Tp, _ValueT,
799  __void_t<decltype(allocator_traits<_Alloc>::construct(
800  std::declval<_Alloc&>(), std::declval<_ValueT*>(),
801  std::declval<_Tp>()))>>
802  : true_type
803  { };
804 
805  // true if _Alloc::value_type is CopyInsertable into containers using _Alloc
806  // (might be wrong if _Alloc::construct exists but is not constrained,
807  // i.e. actually trying to use it would still be invalid. Use with caution.)
808  template<typename _Alloc>
809  struct __is_copy_insertable
810  : __is_alloc_insertable_impl<_Alloc,
811  typename _Alloc::value_type const&>::type
812  { };
813 
814 #if _GLIBCXX_HOSTED
815  // std::allocator<_Tp> just requires CopyConstructible
816  template<typename _Tp>
817  struct __is_copy_insertable<allocator<_Tp>>
818  : is_copy_constructible<_Tp>
819  { };
820 #endif
821 
822  // true if _Alloc::value_type is MoveInsertable into containers using _Alloc
823  // (might be wrong if _Alloc::construct exists but is not constrained,
824  // i.e. actually trying to use it would still be invalid. Use with caution.)
825  template<typename _Alloc>
826  struct __is_move_insertable
827  : __is_alloc_insertable_impl<_Alloc, typename _Alloc::value_type>::type
828  { };
829 
830 #if _GLIBCXX_HOSTED
831  // std::allocator<_Tp> just requires MoveConstructible
832  template<typename _Tp>
833  struct __is_move_insertable<allocator<_Tp>>
834  : is_move_constructible<_Tp>
835  { };
836 #endif
837 
838  // Trait to detect Allocator-like types.
839  template<typename _Alloc, typename = void>
840  struct __is_allocator : false_type { };
841 
842  template<typename _Alloc>
843  struct __is_allocator<_Alloc,
844  __void_t<typename _Alloc::value_type,
845  decltype(std::declval<_Alloc&>().allocate(size_t{}))>>
846  : true_type { };
847 
848  template<typename _Alloc>
849  using _RequireAllocator
850  = typename enable_if<__is_allocator<_Alloc>::value, _Alloc>::type;
851 
852  template<typename _Alloc>
853  using _RequireNotAllocator
854  = typename enable_if<!__is_allocator<_Alloc>::value, _Alloc>::type;
855 
856 #if __cpp_concepts >= 201907L
857  template<typename _Alloc>
858  concept __allocator_like = requires (_Alloc& __a) {
859  typename _Alloc::value_type;
860  __a.deallocate(__a.allocate(1u), 1u);
861  };
862 #endif
863  /// @endcond
864 #endif // C++11
865 
866  /// @cond undocumented
867 
868  // To implement Option 3 of DR 431.
869  template<typename _Alloc, bool = __is_empty(_Alloc)>
870  struct __alloc_swap
871  { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } };
872 
873  template<typename _Alloc>
874  struct __alloc_swap<_Alloc, false>
875  {
876  static void
877  _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT
878  {
879  // Precondition: swappable allocators.
880  if (__one != __two)
881  swap(__one, __two);
882  }
883  };
884 
885 #if __cplusplus >= 201103L
886  template<typename _Tp, bool
887  = __or_<is_copy_constructible<typename _Tp::value_type>,
888  is_nothrow_move_constructible<typename _Tp::value_type>>::value>
889  struct __shrink_to_fit_aux
890  { static bool _S_do_it(_Tp&) noexcept { return false; } };
891 
892  template<typename _Tp>
893  struct __shrink_to_fit_aux<_Tp, true>
894  {
895  _GLIBCXX20_CONSTEXPR
896  static bool
897  _S_do_it(_Tp& __c) noexcept
898  {
899 #if __cpp_exceptions
900  try
901  {
902  _Tp(__make_move_if_noexcept_iterator(__c.begin()),
903  __make_move_if_noexcept_iterator(__c.end()),
904  __c.get_allocator()).swap(__c);
905  return true;
906  }
907  catch(...)
908  { return false; }
909 #else
910  return false;
911 #endif
912  }
913  };
914 #endif
915 
916  /**
917  * Destroy a range of objects using the supplied allocator. For
918  * non-default allocators we do not optimize away invocation of
919  * destroy() even if _Tp has a trivial destructor.
920  */
921 
922  template<typename _ForwardIterator, typename _Allocator>
923  _GLIBCXX20_CONSTEXPR
924  void
925  _Destroy(_ForwardIterator __first, _ForwardIterator __last,
926  _Allocator& __alloc)
927  {
928  for (; __first != __last; ++__first)
929 #if __cplusplus < 201103L
930  __alloc.destroy(std::__addressof(*__first));
931 #else
933  std::__addressof(*__first));
934 #endif
935  }
936 
937 #if _GLIBCXX_HOSTED
938  template<typename _ForwardIterator, typename _Tp>
939  __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR
940  inline void
941  _Destroy(_ForwardIterator __first, _ForwardIterator __last,
942  allocator<_Tp>&)
943  {
944  std::_Destroy(__first, __last);
945  }
946 #endif
947  /// @endcond
948 
949 _GLIBCXX_END_NAMESPACE_VERSION
950 } // namespace std
951 #endif // _ALLOC_TRAITS_H
__bool_constant< true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:111
__bool_constant< false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:114
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:51
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:126
ISO C++ entities toplevel namespace is std.
constexpr void _Construct(_Tp *__p, _Args &&... __args)
constexpr void _Destroy(_ForwardIterator __first, _ForwardIterator __last)
is_nothrow_destructible
Definition: type_traits:1102
is_nothrow_constructible
Definition: type_traits:1185
Uniform interface to all allocator types.
static constexpr auto construct(_Alloc &__a, _Tp *__p, _Args &&... __args) noexcept(noexcept(_S_construct(__a, __p, std::forward< _Args >(__args)...))) -> decltype(_S_construct(__a, __p, std::forward< _Args >(__args)...))
Construct an object of type _Tp
__detected_or_t< false_type, __pocma, _Alloc > propagate_on_container_move_assignment
How the allocator is propagated on move assignment.
typename _Ptr< __v_pointer, void >::type void_pointer
The allocator's void pointer type.
__detected_or_t< value_type *, __pointer, _Alloc > pointer
The allocator's pointer type.
static constexpr pointer allocate(_Alloc &__a, size_type __n)
Allocate memory.
static constexpr pointer allocate(_Alloc &__a, size_type __n, const_void_pointer __hint)
Allocate memory.
typename _Size< _Alloc, difference_type >::type size_type
The allocator's size type.
typename _Ptr< __cv_pointer, const void >::type const_void_pointer
The allocator's const void pointer type.
typename _Diff< _Alloc, pointer >::type difference_type
The allocator's difference type.
typename _Ptr< __c_pointer, const value_type >::type const_pointer
The allocator's const pointer type.
_Alloc::value_type value_type
The allocated type.
static constexpr void deallocate(_Alloc &__a, pointer __p, size_type __n)
Deallocate memory.
typename __detected_or_t< is_empty< _Alloc >, __equal, _Alloc >::type is_always_equal
Whether all instances of the allocator type compare equal.
static constexpr size_type max_size(const _Alloc &__a) noexcept
The maximum supported allocation size.
__detected_or_t< false_type, __pocca, _Alloc > propagate_on_container_copy_assignment
How the allocator is propagated on copy assignment.
static constexpr void destroy(_Alloc &__a, _Tp *__p) noexcept(noexcept(_S_destroy(__a, __p, 0)))
Destroy an object of type _Tp.
static constexpr _Alloc select_on_container_copy_construction(const _Alloc &__rhs)
Obtain an allocator to use when copying a container.
__detected_or_t< false_type, __pocs, _Alloc > propagate_on_container_swap
How the allocator is propagated on swap.
_Alloc allocator_type
The allocator type.
static constexpr pointer allocate(allocator_type &__a, size_type __n, [[maybe_unused]] const_void_pointer __hint)
Allocate memory.
allocator< _Tp > allocator_type
The allocator type.
void * void_pointer
The allocator's void pointer type.
_Tp * pointer
The allocator's pointer type.
false_type propagate_on_container_swap
How the allocator is propagated on swap.
static constexpr pointer allocate(allocator_type &__a, size_type __n)
Allocate memory.
std::ptrdiff_t difference_type
The allocator's difference type.
true_type is_always_equal
Whether all instances of the allocator type compare equal.
const _Tp * const_pointer
The allocator's const pointer type.
const void * const_void_pointer
The allocator's const void pointer type.
true_type propagate_on_container_move_assignment
How the allocator is propagated on move assignment.
static constexpr void deallocate(allocator_type &__a, pointer __p, size_type __n)
Deallocate memory.
static constexpr size_type max_size(const allocator_type &__a) noexcept
The maximum supported allocation size.
static constexpr allocator_type select_on_container_copy_construction(const allocator_type &__rhs)
Obtain an allocator to use when copying a container.
static constexpr void construct(allocator_type &__a, _Up *__p, _Args &&... __args) noexcept(std::is_nothrow_constructible< _Up, _Args... >::value)
Construct an object of type _Up
static constexpr void destroy(allocator_type &__a, _Up *__p) noexcept(is_nothrow_destructible< _Up >::value)
Destroy an object of type _Up.
false_type propagate_on_container_copy_assignment
How the allocator is propagated on copy assignment.
std::size_t size_type
The allocator's size type.
false_type propagate_on_container_copy_assignment
How the allocator is propagated on copy assignment.
void * pointer
The allocator's pointer type.
void * void_pointer
The allocator's void pointer type.
static void deallocate(allocator_type &, void *, size_type)=delete
deallocate is ill-formed for allocator<void>
static constexpr void construct(allocator_type &, _Up *__p, _Args &&... __args) noexcept(std::is_nothrow_constructible< _Up, _Args... >::value)
Construct an object of type _Up
true_type is_always_equal
Whether all instances of the allocator type compare equal.
static size_type max_size(const allocator_type &)=delete
max_size is ill-formed for allocator<void>
std::size_t size_type
The allocator's size type.
true_type propagate_on_container_move_assignment
How the allocator is propagated on move assignment.
const void * const_pointer
The allocator's const pointer type.
static void * allocate(allocator_type &, size_type, const void *=nullptr)=delete
allocate is ill-formed for allocator<void>
std::ptrdiff_t difference_type
The allocator's difference type.
static constexpr allocator_type select_on_container_copy_construction(const allocator_type &__rhs)
Obtain an allocator to use when copying a container.
const void * const_void_pointer
The allocator's const void pointer type.
static constexpr void destroy(allocator_type &, _Up *__p) noexcept(is_nothrow_destructible< _Up >::value)
Destroy an object of type _Up
false_type propagate_on_container_swap
How the allocator is propagated on swap.
The standard allocator, as per C++03 [20.4.1].
Definition: allocator.h:129
Uniform interface to all pointer-like types.
Definition: ptr_traits.h:178