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[1166]1// Allocator traits -*- C++ -*-
2
3// Copyright (C) 2011-2021 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 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/allocator.h>
37# include <bits/ptr_traits.h>
38# include <ext/numeric_traits.h>
39#endif
40
41namespace std _GLIBCXX_VISIBILITY(default)
42{
43_GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45#if __cplusplus >= 201103L
46#define __cpp_lib_allocator_traits_is_always_equal 201411
47
48 struct __allocator_traits_base
49 {
50 template<typename _Tp, typename _Up, typename = void>
51 struct __rebind : __replace_first_arg<_Tp, _Up> { };
52
53 template<typename _Tp, typename _Up>
54 struct __rebind<_Tp, _Up,
55 __void_t<typename _Tp::template rebind<_Up>::other>>
56 { using type = typename _Tp::template rebind<_Up>::other; };
57
58 protected:
59 template<typename _Tp>
60 using __pointer = typename _Tp::pointer;
61 template<typename _Tp>
62 using __c_pointer = typename _Tp::const_pointer;
63 template<typename _Tp>
64 using __v_pointer = typename _Tp::void_pointer;
65 template<typename _Tp>
66 using __cv_pointer = typename _Tp::const_void_pointer;
67 template<typename _Tp>
68 using __pocca = typename _Tp::propagate_on_container_copy_assignment;
69 template<typename _Tp>
70 using __pocma = typename _Tp::propagate_on_container_move_assignment;
71 template<typename _Tp>
72 using __pocs = typename _Tp::propagate_on_container_swap;
73 template<typename _Tp>
74 using __equal = typename _Tp::is_always_equal;
75 };
76
77 template<typename _Alloc, typename _Up>
78 using __alloc_rebind
79 = typename __allocator_traits_base::template __rebind<_Alloc, _Up>::type;
80
81 /**
82 * @brief Uniform interface to all allocator types.
83 * @ingroup allocators
84 */
85 template<typename _Alloc>
86 struct allocator_traits : __allocator_traits_base
87 {
88 /// The allocator type
89 typedef _Alloc allocator_type;
90 /// The allocated type
91 typedef typename _Alloc::value_type value_type;
92
93 /**
94 * @brief The allocator's pointer type.
95 *
96 * @c Alloc::pointer if that type exists, otherwise @c value_type*
97 */
98 using pointer = __detected_or_t<value_type*, __pointer, _Alloc>;
99
100 private:
101 // Select _Func<_Alloc> or pointer_traits<pointer>::rebind<_Tp>
102 template<template<typename> class _Func, typename _Tp, typename = void>
103 struct _Ptr
104 {
105 using type = typename pointer_traits<pointer>::template rebind<_Tp>;
106 };
107
108 template<template<typename> class _Func, typename _Tp>
109 struct _Ptr<_Func, _Tp, __void_t<_Func<_Alloc>>>
110 {
111 using type = _Func<_Alloc>;
112 };
113
114 // Select _A2::difference_type or pointer_traits<_Ptr>::difference_type
115 template<typename _A2, typename _PtrT, typename = void>
116 struct _Diff
117 { using type = typename pointer_traits<_PtrT>::difference_type; };
118
119 template<typename _A2, typename _PtrT>
120 struct _Diff<_A2, _PtrT, __void_t<typename _A2::difference_type>>
121 { using type = typename _A2::difference_type; };
122
123 // Select _A2::size_type or make_unsigned<_DiffT>::type
124 template<typename _A2, typename _DiffT, typename = void>
125 struct _Size : make_unsigned<_DiffT> { };
126
127 template<typename _A2, typename _DiffT>
128 struct _Size<_A2, _DiffT, __void_t<typename _A2::size_type>>
129 { using type = typename _A2::size_type; };
130
131 public:
132 /**
133 * @brief The allocator's const pointer type.
134 *
135 * @c Alloc::const_pointer if that type exists, otherwise
136 * <tt> pointer_traits<pointer>::rebind<const value_type> </tt>
137 */
138 using const_pointer = typename _Ptr<__c_pointer, const value_type>::type;
139
140 /**
141 * @brief The allocator's void pointer type.
142 *
143 * @c Alloc::void_pointer if that type exists, otherwise
144 * <tt> pointer_traits<pointer>::rebind<void> </tt>
145 */
146 using void_pointer = typename _Ptr<__v_pointer, void>::type;
147
148 /**
149 * @brief The allocator's const void pointer type.
150 *
151 * @c Alloc::const_void_pointer if that type exists, otherwise
152 * <tt> pointer_traits<pointer>::rebind<const void> </tt>
153 */
154 using const_void_pointer = typename _Ptr<__cv_pointer, const void>::type;
155
156 /**
157 * @brief The allocator's difference type
158 *
159 * @c Alloc::difference_type if that type exists, otherwise
160 * <tt> pointer_traits<pointer>::difference_type </tt>
161 */
162 using difference_type = typename _Diff<_Alloc, pointer>::type;
163
164 /**
165 * @brief The allocator's size type
166 *
167 * @c Alloc::size_type if that type exists, otherwise
168 * <tt> make_unsigned<difference_type>::type </tt>
169 */
170 using size_type = typename _Size<_Alloc, difference_type>::type;
171
172 /**
173 * @brief How the allocator is propagated on copy assignment
174 *
175 * @c Alloc::propagate_on_container_copy_assignment if that type exists,
176 * otherwise @c false_type
177 */
178 using propagate_on_container_copy_assignment
179 = __detected_or_t<false_type, __pocca, _Alloc>;
180
181 /**
182 * @brief How the allocator is propagated on move assignment
183 *
184 * @c Alloc::propagate_on_container_move_assignment if that type exists,
185 * otherwise @c false_type
186 */
187 using propagate_on_container_move_assignment
188 = __detected_or_t<false_type, __pocma, _Alloc>;
189
190 /**
191 * @brief How the allocator is propagated on swap
192 *
193 * @c Alloc::propagate_on_container_swap if that type exists,
194 * otherwise @c false_type
195 */
196 using propagate_on_container_swap
197 = __detected_or_t<false_type, __pocs, _Alloc>;
198
199 /**
200 * @brief Whether all instances of the allocator type compare equal.
201 *
202 * @c Alloc::is_always_equal if that type exists,
203 * otherwise @c is_empty<Alloc>::type
204 */
205 using is_always_equal
206 = __detected_or_t<typename is_empty<_Alloc>::type, __equal, _Alloc>;
207
208 template<typename _Tp>
209 using rebind_alloc = __alloc_rebind<_Alloc, _Tp>;
210 template<typename _Tp>
211 using rebind_traits = allocator_traits<rebind_alloc<_Tp>>;
212
213 private:
214 template<typename _Alloc2>
215 static constexpr auto
216 _S_allocate(_Alloc2& __a, size_type __n, const_void_pointer __hint, int)
217 -> decltype(__a.allocate(__n, __hint))
218 { return __a.allocate(__n, __hint); }
219
220 template<typename _Alloc2>
221 static constexpr pointer
222 _S_allocate(_Alloc2& __a, size_type __n, const_void_pointer, ...)
223 { return __a.allocate(__n); }
224
225 template<typename _Tp, typename... _Args>
226 struct __construct_helper
227 {
228 template<typename _Alloc2,
229 typename = decltype(std::declval<_Alloc2*>()->construct(
230 std::declval<_Tp*>(), std::declval<_Args>()...))>
231 static true_type __test(int);
232
233 template<typename>
234 static false_type __test(...);
235
236 using type = decltype(__test<_Alloc>(0));
237 };
238
239 template<typename _Tp, typename... _Args>
240 using __has_construct
241 = typename __construct_helper<_Tp, _Args...>::type;
242
243 template<typename _Tp, typename... _Args>
244 static _GLIBCXX14_CONSTEXPR _Require<__has_construct<_Tp, _Args...>>
245 _S_construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
246 noexcept(noexcept(__a.construct(__p, std::forward<_Args>(__args)...)))
247 { __a.construct(__p, std::forward<_Args>(__args)...); }
248
249 template<typename _Tp, typename... _Args>
250 static _GLIBCXX14_CONSTEXPR
251 _Require<__and_<__not_<__has_construct<_Tp, _Args...>>,
252 is_constructible<_Tp, _Args...>>>
253 _S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
254 noexcept(std::is_nothrow_constructible<_Tp, _Args...>::value)
255 {
256#if __cplusplus <= 201703L
257 ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
258#else
259 std::construct_at(__p, std::forward<_Args>(__args)...);
260#endif
261 }
262
263 template<typename _Alloc2, typename _Tp>
264 static _GLIBCXX14_CONSTEXPR auto
265 _S_destroy(_Alloc2& __a, _Tp* __p, int)
266 noexcept(noexcept(__a.destroy(__p)))
267 -> decltype(__a.destroy(__p))
268 { __a.destroy(__p); }
269
270 template<typename _Alloc2, typename _Tp>
271 static _GLIBCXX14_CONSTEXPR void
272 _S_destroy(_Alloc2&, _Tp* __p, ...)
273 noexcept(std::is_nothrow_destructible<_Tp>::value)
274 { std::_Destroy(__p); }
275
276 template<typename _Alloc2>
277 static constexpr auto
278 _S_max_size(_Alloc2& __a, int)
279 -> decltype(__a.max_size())
280 { return __a.max_size(); }
281
282 template<typename _Alloc2>
283 static constexpr size_type
284 _S_max_size(_Alloc2&, ...)
285 {
286 // _GLIBCXX_RESOLVE_LIB_DEFECTS
287 // 2466. allocator_traits::max_size() default behavior is incorrect
288 return __gnu_cxx::__numeric_traits<size_type>::__max
289 / sizeof(value_type);
290 }
291
292 template<typename _Alloc2>
293 static constexpr auto
294 _S_select(_Alloc2& __a, int)
295 -> decltype(__a.select_on_container_copy_construction())
296 { return __a.select_on_container_copy_construction(); }
297
298 template<typename _Alloc2>
299 static constexpr _Alloc2
300 _S_select(_Alloc2& __a, ...)
301 { return __a; }
302
303 public:
304
305 /**
306 * @brief Allocate memory.
307 * @param __a An allocator.
308 * @param __n The number of objects to allocate space for.
309 *
310 * Calls @c a.allocate(n)
311 */
312 _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
313 allocate(_Alloc& __a, size_type __n)
314 { return __a.allocate(__n); }
315
316 /**
317 * @brief Allocate memory.
318 * @param __a An allocator.
319 * @param __n The number of objects to allocate space for.
320 * @param __hint Aid to locality.
321 * @return Memory of suitable size and alignment for @a n objects
322 * of type @c value_type
323 *
324 * Returns <tt> a.allocate(n, hint) </tt> if that expression is
325 * well-formed, otherwise returns @c a.allocate(n)
326 */
327 _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
328 allocate(_Alloc& __a, size_type __n, const_void_pointer __hint)
329 { return _S_allocate(__a, __n, __hint, 0); }
330
331 /**
332 * @brief Deallocate memory.
333 * @param __a An allocator.
334 * @param __p Pointer to the memory to deallocate.
335 * @param __n The number of objects space was allocated for.
336 *
337 * Calls <tt> a.deallocate(p, n) </tt>
338 */
339 static _GLIBCXX20_CONSTEXPR void
340 deallocate(_Alloc& __a, pointer __p, size_type __n)
341 { __a.deallocate(__p, __n); }
342
343 /**
344 * @brief Construct an object of type `_Tp`
345 * @param __a An allocator.
346 * @param __p Pointer to memory of suitable size and alignment for Tp
347 * @param __args Constructor arguments.
348 *
349 * Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
350 * if that expression is well-formed, otherwise uses placement-new
351 * to construct an object of type @a _Tp at location @a __p from the
352 * arguments @a __args...
353 */
354 template<typename _Tp, typename... _Args>
355 static _GLIBCXX20_CONSTEXPR auto
356 construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
357 noexcept(noexcept(_S_construct(__a, __p,
358 std::forward<_Args>(__args)...)))
359 -> decltype(_S_construct(__a, __p, std::forward<_Args>(__args)...))
360 { _S_construct(__a, __p, std::forward<_Args>(__args)...); }
361
362 /**
363 * @brief Destroy an object of type @a _Tp
364 * @param __a An allocator.
365 * @param __p Pointer to the object to destroy
366 *
367 * Calls @c __a.destroy(__p) if that expression is well-formed,
368 * otherwise calls @c __p->~_Tp()
369 */
370 template<typename _Tp>
371 static _GLIBCXX20_CONSTEXPR void
372 destroy(_Alloc& __a, _Tp* __p)
373 noexcept(noexcept(_S_destroy(__a, __p, 0)))
374 { _S_destroy(__a, __p, 0); }
375
376 /**
377 * @brief The maximum supported allocation size
378 * @param __a An allocator.
379 * @return @c __a.max_size() or @c numeric_limits<size_type>::max()
380 *
381 * Returns @c __a.max_size() if that expression is well-formed,
382 * otherwise returns @c numeric_limits<size_type>::max()
383 */
384 static _GLIBCXX20_CONSTEXPR size_type
385 max_size(const _Alloc& __a) noexcept
386 { return _S_max_size(__a, 0); }
387
388 /**
389 * @brief Obtain an allocator to use when copying a container.
390 * @param __rhs An allocator.
391 * @return @c __rhs.select_on_container_copy_construction() or @a __rhs
392 *
393 * Returns @c __rhs.select_on_container_copy_construction() if that
394 * expression is well-formed, otherwise returns @a __rhs
395 */
396 static _GLIBCXX20_CONSTEXPR _Alloc
397 select_on_container_copy_construction(const _Alloc& __rhs)
398 { return _S_select(__rhs, 0); }
399 };
400
401#if __cplusplus > 201703L
402# define __cpp_lib_constexpr_dynamic_alloc 201907L
403#endif
404
405 /// Partial specialization for std::allocator.
406 template<typename _Tp>
407 struct allocator_traits<allocator<_Tp>>
408 {
409 /// The allocator type
410 using allocator_type = allocator<_Tp>;
411
412 /// The allocated type
413 using value_type = _Tp;
414
415 /// The allocator's pointer type.
416 using pointer = _Tp*;
417
418 /// The allocator's const pointer type.
419 using const_pointer = const _Tp*;
420
421 /// The allocator's void pointer type.
422 using void_pointer = void*;
423
424 /// The allocator's const void pointer type.
425 using const_void_pointer = const void*;
426
427 /// The allocator's difference type
428 using difference_type = std::ptrdiff_t;
429
430 /// The allocator's size type
431 using size_type = std::size_t;
432
433 /// How the allocator is propagated on copy assignment
434 using propagate_on_container_copy_assignment = false_type;
435
436 /// How the allocator is propagated on move assignment
437 using propagate_on_container_move_assignment = true_type;
438
439 /// How the allocator is propagated on swap
440 using propagate_on_container_swap = false_type;
441
442 /// Whether all instances of the allocator type compare equal.
443 using is_always_equal = true_type;
444
445 template<typename _Up>
446 using rebind_alloc = allocator<_Up>;
447
448 template<typename _Up>
449 using rebind_traits = allocator_traits<allocator<_Up>>;
450
451 /**
452 * @brief Allocate memory.
453 * @param __a An allocator.
454 * @param __n The number of objects to allocate space for.
455 *
456 * Calls @c a.allocate(n)
457 */
458 _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
459 allocate(allocator_type& __a, size_type __n)
460 { return __a.allocate(__n); }
461
462 /**
463 * @brief Allocate memory.
464 * @param __a An allocator.
465 * @param __n The number of objects to allocate space for.
466 * @param __hint Aid to locality.
467 * @return Memory of suitable size and alignment for @a n objects
468 * of type @c value_type
469 *
470 * Returns <tt> a.allocate(n, hint) </tt>
471 */
472 _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
473 allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
474 {
475#if __cplusplus <= 201703L
476 return __a.allocate(__n, __hint);
477#else
478 return __a.allocate(__n);
479#endif
480 }
481
482 /**
483 * @brief Deallocate memory.
484 * @param __a An allocator.
485 * @param __p Pointer to the memory to deallocate.
486 * @param __n The number of objects space was allocated for.
487 *
488 * Calls <tt> a.deallocate(p, n) </tt>
489 */
490 static _GLIBCXX20_CONSTEXPR void
491 deallocate(allocator_type& __a, pointer __p, size_type __n)
492 { __a.deallocate(__p, __n); }
493
494 /**
495 * @brief Construct an object of type `_Up`
496 * @param __a An allocator.
497 * @param __p Pointer to memory of suitable size and alignment for
498 * an object of type `_Up`.
499 * @param __args Constructor arguments.
500 *
501 * Calls `__a.construct(__p, std::forward<_Args>(__args)...)`
502 * in C++11, C++14 and C++17. Changed in C++20 to call
503 * `std::construct_at(__p, std::forward<_Args>(__args)...)` instead.
504 */
505 template<typename _Up, typename... _Args>
506 static _GLIBCXX20_CONSTEXPR void
507 construct(allocator_type& __a __attribute__((__unused__)), _Up* __p,
508 _Args&&... __args)
509 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
510 {
511#if __cplusplus <= 201703L
512 __a.construct(__p, std::forward<_Args>(__args)...);
513#else
514 std::construct_at(__p, std::forward<_Args>(__args)...);
515#endif
516 }
517
518 /**
519 * @brief Destroy an object of type @a _Up
520 * @param __a An allocator.
521 * @param __p Pointer to the object to destroy
522 *
523 * Calls @c __a.destroy(__p).
524 */
525 template<typename _Up>
526 static _GLIBCXX20_CONSTEXPR void
527 destroy(allocator_type& __a __attribute__((__unused__)), _Up* __p)
528 noexcept(is_nothrow_destructible<_Up>::value)
529 {
530#if __cplusplus <= 201703L
531 __a.destroy(__p);
532#else
533 std::destroy_at(__p);
534#endif
535 }
536
537 /**
538 * @brief The maximum supported allocation size
539 * @param __a An allocator.
540 * @return @c __a.max_size()
541 */
542 static _GLIBCXX20_CONSTEXPR size_type
543 max_size(const allocator_type& __a __attribute__((__unused__))) noexcept
544 {
545#if __cplusplus <= 201703L
546 return __a.max_size();
547#else
548 return size_t(-1) / sizeof(value_type);
549#endif
550 }
551
552 /**
553 * @brief Obtain an allocator to use when copying a container.
554 * @param __rhs An allocator.
555 * @return @c __rhs
556 */
557 static _GLIBCXX20_CONSTEXPR allocator_type
558 select_on_container_copy_construction(const allocator_type& __rhs)
559 { return __rhs; }
560 };
561
562#if __cplusplus < 201703L
563 template<typename _Alloc>
564 inline void
565 __do_alloc_on_copy(_Alloc& __one, const _Alloc& __two, true_type)
566 { __one = __two; }
567
568 template<typename _Alloc>
569 inline void
570 __do_alloc_on_copy(_Alloc&, const _Alloc&, false_type)
571 { }
572#endif
573
574 template<typename _Alloc>
575 _GLIBCXX14_CONSTEXPR inline void
576 __alloc_on_copy(_Alloc& __one, const _Alloc& __two)
577 {
578 typedef allocator_traits<_Alloc> __traits;
579 typedef typename __traits::propagate_on_container_copy_assignment __pocca;
580#if __cplusplus >= 201703L
581 if constexpr (__pocca::value)
582 __one = __two;
583#else
584 __do_alloc_on_copy(__one, __two, __pocca());
585#endif
586 }
587
588 template<typename _Alloc>
589 constexpr _Alloc
590 __alloc_on_copy(const _Alloc& __a)
591 {
592 typedef allocator_traits<_Alloc> __traits;
593 return __traits::select_on_container_copy_construction(__a);
594 }
595
596#if __cplusplus < 201703L
597 template<typename _Alloc>
598 inline void __do_alloc_on_move(_Alloc& __one, _Alloc& __two, true_type)
599 { __one = std::move(__two); }
600
601 template<typename _Alloc>
602 inline void __do_alloc_on_move(_Alloc&, _Alloc&, false_type)
603 { }
604#endif
605
606 template<typename _Alloc>
607 _GLIBCXX14_CONSTEXPR inline void
608 __alloc_on_move(_Alloc& __one, _Alloc& __two)
609 {
610 typedef allocator_traits<_Alloc> __traits;
611 typedef typename __traits::propagate_on_container_move_assignment __pocma;
612#if __cplusplus >= 201703L
613 if constexpr (__pocma::value)
614 __one = std::move(__two);
615#else
616 __do_alloc_on_move(__one, __two, __pocma());
617#endif
618 }
619
620#if __cplusplus < 201703L
621 template<typename _Alloc>
622 inline void __do_alloc_on_swap(_Alloc& __one, _Alloc& __two, true_type)
623 {
624 using std::swap;
625 swap(__one, __two);
626 }
627
628 template<typename _Alloc>
629 inline void __do_alloc_on_swap(_Alloc&, _Alloc&, false_type)
630 { }
631#endif
632
633 template<typename _Alloc>
634 _GLIBCXX14_CONSTEXPR inline void
635 __alloc_on_swap(_Alloc& __one, _Alloc& __two)
636 {
637 typedef allocator_traits<_Alloc> __traits;
638 typedef typename __traits::propagate_on_container_swap __pocs;
639#if __cplusplus >= 201703L
640 if constexpr (__pocs::value)
641 {
642 using std::swap;
643 swap(__one, __two);
644 }
645#else
646 __do_alloc_on_swap(__one, __two, __pocs());
647#endif
648 }
649
650 template<typename _Alloc, typename _Tp,
651 typename _ValueT = __remove_cvref_t<typename _Alloc::value_type>,
652 typename = void>
653 struct __is_alloc_insertable_impl
654 : false_type
655 { };
656
657 template<typename _Alloc, typename _Tp, typename _ValueT>
658 struct __is_alloc_insertable_impl<_Alloc, _Tp, _ValueT,
659 __void_t<decltype(allocator_traits<_Alloc>::construct(
660 std::declval<_Alloc&>(), std::declval<_ValueT*>(),
661 std::declval<_Tp>()))>>
662 : true_type
663 { };
664
665 // true if _Alloc::value_type is CopyInsertable into containers using _Alloc
666 // (might be wrong if _Alloc::construct exists but is not constrained,
667 // i.e. actually trying to use it would still be invalid. Use with caution.)
668 template<typename _Alloc>
669 struct __is_copy_insertable
670 : __is_alloc_insertable_impl<_Alloc,
671 typename _Alloc::value_type const&>::type
672 { };
673
674 // std::allocator<_Tp> just requires CopyConstructible
675 template<typename _Tp>
676 struct __is_copy_insertable<allocator<_Tp>>
677 : is_copy_constructible<_Tp>
678 { };
679
680 // true if _Alloc::value_type is MoveInsertable into containers using _Alloc
681 // (might be wrong if _Alloc::construct exists but is not constrained,
682 // i.e. actually trying to use it would still be invalid. Use with caution.)
683 template<typename _Alloc>
684 struct __is_move_insertable
685 : __is_alloc_insertable_impl<_Alloc, typename _Alloc::value_type>::type
686 { };
687
688 // std::allocator<_Tp> just requires MoveConstructible
689 template<typename _Tp>
690 struct __is_move_insertable<allocator<_Tp>>
691 : is_move_constructible<_Tp>
692 { };
693
694 // Trait to detect Allocator-like types.
695 template<typename _Alloc, typename = void>
696 struct __is_allocator : false_type { };
697
698 template<typename _Alloc>
699 struct __is_allocator<_Alloc,
700 __void_t<typename _Alloc::value_type,
701 decltype(std::declval<_Alloc&>().allocate(size_t{}))>>
702 : true_type { };
703
704 template<typename _Alloc>
705 using _RequireAllocator
706 = typename enable_if<__is_allocator<_Alloc>::value, _Alloc>::type;
707
708 template<typename _Alloc>
709 using _RequireNotAllocator
710 = typename enable_if<!__is_allocator<_Alloc>::value, _Alloc>::type;
711
712#if __cpp_concepts >= 201907L
713 template<typename _Alloc>
714 concept __allocator_like = requires (_Alloc& __a) {
715 typename _Alloc::value_type;
716 __a.deallocate(__a.allocate(1u), 1u);
717 };
718#endif
719#endif // C++11
720
721 /**
722 * Destroy a range of objects using the supplied allocator. For
723 * non-default allocators we do not optimize away invocation of
724 * destroy() even if _Tp has a trivial destructor.
725 */
726
727 template<typename _ForwardIterator, typename _Allocator>
728 void
729 _Destroy(_ForwardIterator __first, _ForwardIterator __last,
730 _Allocator& __alloc)
731 {
732 for (; __first != __last; ++__first)
733#if __cplusplus < 201103L
734 __alloc.destroy(std::__addressof(*__first));
735#else
736 allocator_traits<_Allocator>::destroy(__alloc,
737 std::__addressof(*__first));
738#endif
739 }
740
741 template<typename _ForwardIterator, typename _Tp>
742 inline void
743 _Destroy(_ForwardIterator __first, _ForwardIterator __last,
744 allocator<_Tp>&)
745 {
746 _Destroy(__first, __last);
747 }
748
749_GLIBCXX_END_NAMESPACE_VERSION
750} // namespace std
751#endif // _ALLOC_TRAITS_H
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