1 // Allocator traits -*- C++ -*-
3 // Copyright (C) 2011-2019 Free Software Foundation, Inc.
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)
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.
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.
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/>.
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}
30 #ifndef _ALLOC_TRAITS_H
31 #define _ALLOC_TRAITS_H 1
33 #if __cplusplus >= 201103L
35 #include <bits/memoryfwd.h>
36 #include <bits/ptr_traits.h>
37 #include <ext/numeric_traits.h>
39 #define __cpp_lib_allocator_traits_is_always_equal 201411
41 namespace std
_GLIBCXX_VISIBILITY(default)
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
45 struct __allocator_traits_base
47 template<typename _Tp
, typename _Up
, typename
= void>
48 struct __rebind
: __replace_first_arg
<_Tp
, _Up
> { };
50 template<typename _Tp
, typename _Up
>
51 struct __rebind
<_Tp
, _Up
,
52 __void_t
<typename
_Tp::template rebind
<_Up
>::other
>>
53 { using type
= typename
_Tp::template rebind
<_Up
>::other
; };
56 template<typename _Tp
>
57 using __pointer
= typename
_Tp::pointer
;
58 template<typename _Tp
>
59 using __c_pointer
= typename
_Tp::const_pointer
;
60 template<typename _Tp
>
61 using __v_pointer
= typename
_Tp::void_pointer
;
62 template<typename _Tp
>
63 using __cv_pointer
= typename
_Tp::const_void_pointer
;
64 template<typename _Tp
>
65 using __pocca
= typename
_Tp::propagate_on_container_copy_assignment
;
66 template<typename _Tp
>
67 using __pocma
= typename
_Tp::propagate_on_container_move_assignment
;
68 template<typename _Tp
>
69 using __pocs
= typename
_Tp::propagate_on_container_swap
;
70 template<typename _Tp
>
71 using __equal
= typename
_Tp::is_always_equal
;
74 template<typename _Alloc
, typename _Up
>
76 = typename
__allocator_traits_base::template __rebind
<_Alloc
, _Up
>::type
;
79 * @brief Uniform interface to all allocator types.
82 template<typename _Alloc
>
83 struct allocator_traits
: __allocator_traits_base
85 /// The allocator type
86 typedef _Alloc allocator_type
;
87 /// The allocated type
88 typedef typename
_Alloc::value_type value_type
;
91 * @brief The allocator's pointer type.
93 * @c Alloc::pointer if that type exists, otherwise @c value_type*
95 using pointer
= __detected_or_t
<value_type
*, __pointer
, _Alloc
>;
98 // Select _Func<_Alloc> or pointer_traits<pointer>::rebind<_Tp>
99 template<template<typename
> class _Func
, typename _Tp
, typename
= void>
102 using type
= typename pointer_traits
<pointer
>::template rebind
<_Tp
>;
105 template<template<typename
> class _Func
, typename _Tp
>
106 struct _Ptr
<_Func
, _Tp
, __void_t
<_Func
<_Alloc
>>>
108 using type
= _Func
<_Alloc
>;
111 // Select _A2::difference_type or pointer_traits<_Ptr>::difference_type
112 template<typename _A2
, typename _PtrT
, typename
= void>
114 { using type
= typename pointer_traits
<_PtrT
>::difference_type
; };
116 template<typename _A2
, typename _PtrT
>
117 struct _Diff
<_A2
, _PtrT
, __void_t
<typename
_A2::difference_type
>>
118 { using type
= typename
_A2::difference_type
; };
120 // Select _A2::size_type or make_unsigned<_DiffT>::type
121 template<typename _A2
, typename _DiffT
, typename
= void>
122 struct _Size
: make_unsigned
<_DiffT
> { };
124 template<typename _A2
, typename _DiffT
>
125 struct _Size
<_A2
, _DiffT
, __void_t
<typename
_A2::size_type
>>
126 { using type
= typename
_A2::size_type
; };
130 * @brief The allocator's const pointer type.
132 * @c Alloc::const_pointer if that type exists, otherwise
133 * <tt> pointer_traits<pointer>::rebind<const value_type> </tt>
135 using const_pointer
= typename _Ptr
<__c_pointer
, const value_type
>::type
;
138 * @brief The allocator's void pointer type.
140 * @c Alloc::void_pointer if that type exists, otherwise
141 * <tt> pointer_traits<pointer>::rebind<void> </tt>
143 using void_pointer
= typename _Ptr
<__v_pointer
, void>::type
;
146 * @brief The allocator's const void pointer type.
148 * @c Alloc::const_void_pointer if that type exists, otherwise
149 * <tt> pointer_traits<pointer>::rebind<const void> </tt>
151 using const_void_pointer
= typename _Ptr
<__cv_pointer
, const void>::type
;
154 * @brief The allocator's difference type
156 * @c Alloc::difference_type if that type exists, otherwise
157 * <tt> pointer_traits<pointer>::difference_type </tt>
159 using difference_type
= typename _Diff
<_Alloc
, pointer
>::type
;
162 * @brief The allocator's size type
164 * @c Alloc::size_type if that type exists, otherwise
165 * <tt> make_unsigned<difference_type>::type </tt>
167 using size_type
= typename _Size
<_Alloc
, difference_type
>::type
;
170 * @brief How the allocator is propagated on copy assignment
172 * @c Alloc::propagate_on_container_copy_assignment if that type exists,
173 * otherwise @c false_type
175 using propagate_on_container_copy_assignment
176 = __detected_or_t
<false_type
, __pocca
, _Alloc
>;
179 * @brief How the allocator is propagated on move assignment
181 * @c Alloc::propagate_on_container_move_assignment if that type exists,
182 * otherwise @c false_type
184 using propagate_on_container_move_assignment
185 = __detected_or_t
<false_type
, __pocma
, _Alloc
>;
188 * @brief How the allocator is propagated on swap
190 * @c Alloc::propagate_on_container_swap if that type exists,
191 * otherwise @c false_type
193 using propagate_on_container_swap
194 = __detected_or_t
<false_type
, __pocs
, _Alloc
>;
197 * @brief Whether all instances of the allocator type compare equal.
199 * @c Alloc::is_always_equal if that type exists,
200 * otherwise @c is_empty<Alloc>::type
202 using is_always_equal
203 = __detected_or_t
<typename is_empty
<_Alloc
>::type
, __equal
, _Alloc
>;
205 template<typename _Tp
>
206 using rebind_alloc
= __alloc_rebind
<_Alloc
, _Tp
>;
207 template<typename _Tp
>
208 using rebind_traits
= allocator_traits
<rebind_alloc
<_Tp
>>;
211 template<typename _Alloc2
>
213 _S_allocate(_Alloc2
& __a
, size_type __n
, const_void_pointer __hint
, int)
214 -> decltype(__a
.allocate(__n
, __hint
))
215 { return __a
.allocate(__n
, __hint
); }
217 template<typename _Alloc2
>
219 _S_allocate(_Alloc2
& __a
, size_type __n
, const_void_pointer
, ...)
220 { return __a
.allocate(__n
); }
222 template<typename _Tp
, typename
... _Args
>
223 struct __construct_helper
225 template<typename _Alloc2
,
226 typename
= decltype(std::declval
<_Alloc2
*>()->construct(
227 std::declval
<_Tp
*>(), std::declval
<_Args
>()...))>
228 static true_type
__test(int);
231 static false_type
__test(...);
233 using type
= decltype(__test
<_Alloc
>(0));
236 template<typename _Tp
, typename
... _Args
>
237 using __has_construct
238 = typename __construct_helper
<_Tp
, _Args
...>::type
;
240 template<typename _Tp
, typename
... _Args
>
241 static _Require
<__has_construct
<_Tp
, _Args
...>>
242 _S_construct(_Alloc
& __a
, _Tp
* __p
, _Args
&&... __args
)
243 noexcept(noexcept(__a
.construct(__p
, std::forward
<_Args
>(__args
)...)))
244 { __a
.construct(__p
, std::forward
<_Args
>(__args
)...); }
246 template<typename _Tp
, typename
... _Args
>
248 _Require
<__and_
<__not_
<__has_construct
<_Tp
, _Args
...>>,
249 is_constructible
<_Tp
, _Args
...>>>
250 _S_construct(_Alloc
&, _Tp
* __p
, _Args
&&... __args
)
251 noexcept(noexcept(::new((void*)__p
)
252 _Tp(std::forward
<_Args
>(__args
)...)))
253 { ::new((void*)__p
) _Tp(std::forward
<_Args
>(__args
)...); }
255 template<typename _Alloc2
, typename _Tp
>
257 _S_destroy(_Alloc2
& __a
, _Tp
* __p
, int)
258 noexcept(noexcept(__a
.destroy(__p
)))
259 -> decltype(__a
.destroy(__p
))
260 { __a
.destroy(__p
); }
262 template<typename _Alloc2
, typename _Tp
>
264 _S_destroy(_Alloc2
&, _Tp
* __p
, ...)
265 noexcept(noexcept(__p
->~_Tp()))
268 template<typename _Alloc2
>
270 _S_max_size(_Alloc2
& __a
, int)
271 -> decltype(__a
.max_size())
272 { return __a
.max_size(); }
274 template<typename _Alloc2
>
276 _S_max_size(_Alloc2
&, ...)
278 // _GLIBCXX_RESOLVE_LIB_DEFECTS
279 // 2466. allocator_traits::max_size() default behavior is incorrect
280 return __gnu_cxx::__numeric_traits
<size_type
>::__max
281 / sizeof(value_type
);
284 template<typename _Alloc2
>
286 _S_select(_Alloc2
& __a
, int)
287 -> decltype(__a
.select_on_container_copy_construction())
288 { return __a
.select_on_container_copy_construction(); }
290 template<typename _Alloc2
>
292 _S_select(_Alloc2
& __a
, ...)
298 * @brief Allocate memory.
299 * @param __a An allocator.
300 * @param __n The number of objects to allocate space for.
302 * Calls @c a.allocate(n)
304 _GLIBCXX_NODISCARD
static pointer
305 allocate(_Alloc
& __a
, size_type __n
)
306 { return __a
.allocate(__n
); }
309 * @brief Allocate memory.
310 * @param __a An allocator.
311 * @param __n The number of objects to allocate space for.
312 * @param __hint Aid to locality.
313 * @return Memory of suitable size and alignment for @a n objects
314 * of type @c value_type
316 * Returns <tt> a.allocate(n, hint) </tt> if that expression is
317 * well-formed, otherwise returns @c a.allocate(n)
319 _GLIBCXX_NODISCARD
static pointer
320 allocate(_Alloc
& __a
, size_type __n
, const_void_pointer __hint
)
321 { return _S_allocate(__a
, __n
, __hint
, 0); }
324 * @brief Deallocate memory.
325 * @param __a An allocator.
326 * @param __p Pointer to the memory to deallocate.
327 * @param __n The number of objects space was allocated for.
329 * Calls <tt> a.deallocate(p, n) </tt>
332 deallocate(_Alloc
& __a
, pointer __p
, size_type __n
)
333 { __a
.deallocate(__p
, __n
); }
336 * @brief Construct an object of type @a _Tp
337 * @param __a An allocator.
338 * @param __p Pointer to memory of suitable size and alignment for Tp
339 * @param __args Constructor arguments.
341 * Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
342 * if that expression is well-formed, otherwise uses placement-new
343 * to construct an object of type @a _Tp at location @a __p from the
344 * arguments @a __args...
346 template<typename _Tp
, typename
... _Args
>
347 static auto construct(_Alloc
& __a
, _Tp
* __p
, _Args
&&... __args
)
348 noexcept(noexcept(_S_construct(__a
, __p
,
349 std::forward
<_Args
>(__args
)...)))
350 -> decltype(_S_construct(__a
, __p
, std::forward
<_Args
>(__args
)...))
351 { _S_construct(__a
, __p
, std::forward
<_Args
>(__args
)...); }
354 * @brief Destroy an object of type @a _Tp
355 * @param __a An allocator.
356 * @param __p Pointer to the object to destroy
358 * Calls @c __a.destroy(__p) if that expression is well-formed,
359 * otherwise calls @c __p->~_Tp()
361 template<typename _Tp
>
362 static void destroy(_Alloc
& __a
, _Tp
* __p
)
363 noexcept(noexcept(_S_destroy(__a
, __p
, 0)))
364 { _S_destroy(__a
, __p
, 0); }
367 * @brief The maximum supported allocation size
368 * @param __a An allocator.
369 * @return @c __a.max_size() or @c numeric_limits<size_type>::max()
371 * Returns @c __a.max_size() if that expression is well-formed,
372 * otherwise returns @c numeric_limits<size_type>::max()
374 static size_type
max_size(const _Alloc
& __a
) noexcept
375 { return _S_max_size(__a
, 0); }
378 * @brief Obtain an allocator to use when copying a container.
379 * @param __rhs An allocator.
380 * @return @c __rhs.select_on_container_copy_construction() or @a __rhs
382 * Returns @c __rhs.select_on_container_copy_construction() if that
383 * expression is well-formed, otherwise returns @a __rhs
386 select_on_container_copy_construction(const _Alloc
& __rhs
)
387 { return _S_select(__rhs
, 0); }
390 /// Partial specialization for std::allocator.
391 template<typename _Tp
>
392 struct allocator_traits
<allocator
<_Tp
>>
394 /// The allocator type
395 using allocator_type
= allocator
<_Tp
>;
396 /// The allocated type
397 using value_type
= _Tp
;
399 /// The allocator's pointer type.
400 using pointer
= _Tp
*;
402 /// The allocator's const pointer type.
403 using const_pointer
= const _Tp
*;
405 /// The allocator's void pointer type.
406 using void_pointer
= void*;
408 /// The allocator's const void pointer type.
409 using const_void_pointer
= const void*;
411 /// The allocator's difference type
412 using difference_type
= std::ptrdiff_t;
414 /// The allocator's size type
415 using size_type
= std::size_t;
417 /// How the allocator is propagated on copy assignment
418 using propagate_on_container_copy_assignment
= false_type
;
420 /// How the allocator is propagated on move assignment
421 using propagate_on_container_move_assignment
= true_type
;
423 /// How the allocator is propagated on swap
424 using propagate_on_container_swap
= false_type
;
426 /// Whether all instances of the allocator type compare equal.
427 using is_always_equal
= true_type
;
429 template<typename _Up
>
430 using rebind_alloc
= allocator
<_Up
>;
432 template<typename _Up
>
433 using rebind_traits
= allocator_traits
<allocator
<_Up
>>;
436 * @brief Allocate memory.
437 * @param __a An allocator.
438 * @param __n The number of objects to allocate space for.
440 * Calls @c a.allocate(n)
442 _GLIBCXX_NODISCARD
static pointer
443 allocate(allocator_type
& __a
, size_type __n
)
444 { return __a
.allocate(__n
); }
447 * @brief Allocate memory.
448 * @param __a An allocator.
449 * @param __n The number of objects to allocate space for.
450 * @param __hint Aid to locality.
451 * @return Memory of suitable size and alignment for @a n objects
452 * of type @c value_type
454 * Returns <tt> a.allocate(n, hint) </tt>
456 _GLIBCXX_NODISCARD
static pointer
457 allocate(allocator_type
& __a
, size_type __n
, const_void_pointer __hint
)
458 { return __a
.allocate(__n
, __hint
); }
461 * @brief Deallocate memory.
462 * @param __a An allocator.
463 * @param __p Pointer to the memory to deallocate.
464 * @param __n The number of objects space was allocated for.
466 * Calls <tt> a.deallocate(p, n) </tt>
469 deallocate(allocator_type
& __a
, pointer __p
, size_type __n
)
470 { __a
.deallocate(__p
, __n
); }
473 * @brief Construct an object of type @a _Up
474 * @param __a An allocator.
475 * @param __p Pointer to memory of suitable size and alignment for Tp
476 * @param __args Constructor arguments.
478 * Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
480 template<typename _Up
, typename
... _Args
>
482 construct(allocator_type
& __a
, _Up
* __p
, _Args
&&... __args
)
483 noexcept(noexcept(__a
.construct(__p
, std::forward
<_Args
>(__args
)...)))
484 { __a
.construct(__p
, std::forward
<_Args
>(__args
)...); }
487 * @brief Destroy an object of type @a _Up
488 * @param __a An allocator.
489 * @param __p Pointer to the object to destroy
491 * Calls @c __a.destroy(__p).
493 template<typename _Up
>
495 destroy(allocator_type
& __a
, _Up
* __p
)
496 noexcept(noexcept(__a
.destroy(__p
)))
497 { __a
.destroy(__p
); }
500 * @brief The maximum supported allocation size
501 * @param __a An allocator.
502 * @return @c __a.max_size()
505 max_size(const allocator_type
& __a
) noexcept
506 { return __a
.max_size(); }
509 * @brief Obtain an allocator to use when copying a container.
510 * @param __rhs An allocator.
513 static allocator_type
514 select_on_container_copy_construction(const allocator_type
& __rhs
)
519 template<typename _Alloc
>
521 __do_alloc_on_copy(_Alloc
& __one
, const _Alloc
& __two
, true_type
)
524 template<typename _Alloc
>
526 __do_alloc_on_copy(_Alloc
&, const _Alloc
&, false_type
)
529 template<typename _Alloc
>
530 inline void __alloc_on_copy(_Alloc
& __one
, const _Alloc
& __two
)
532 typedef allocator_traits
<_Alloc
> __traits
;
533 typedef typename
__traits::propagate_on_container_copy_assignment __pocca
;
534 __do_alloc_on_copy(__one
, __two
, __pocca());
537 template<typename _Alloc
>
538 inline _Alloc
__alloc_on_copy(const _Alloc
& __a
)
540 typedef allocator_traits
<_Alloc
> __traits
;
541 return __traits::select_on_container_copy_construction(__a
);
544 template<typename _Alloc
>
545 inline void __do_alloc_on_move(_Alloc
& __one
, _Alloc
& __two
, true_type
)
546 { __one
= std::move(__two
); }
548 template<typename _Alloc
>
549 inline void __do_alloc_on_move(_Alloc
&, _Alloc
&, false_type
)
552 template<typename _Alloc
>
553 inline void __alloc_on_move(_Alloc
& __one
, _Alloc
& __two
)
555 typedef allocator_traits
<_Alloc
> __traits
;
556 typedef typename
__traits::propagate_on_container_move_assignment __pocma
;
557 __do_alloc_on_move(__one
, __two
, __pocma());
560 template<typename _Alloc
>
561 inline void __do_alloc_on_swap(_Alloc
& __one
, _Alloc
& __two
, true_type
)
567 template<typename _Alloc
>
568 inline void __do_alloc_on_swap(_Alloc
&, _Alloc
&, false_type
)
571 template<typename _Alloc
>
572 inline void __alloc_on_swap(_Alloc
& __one
, _Alloc
& __two
)
574 typedef allocator_traits
<_Alloc
> __traits
;
575 typedef typename
__traits::propagate_on_container_swap __pocs
;
576 __do_alloc_on_swap(__one
, __two
, __pocs());
579 template<typename _Alloc
, typename _Tp
,
580 typename _ValueT
= __remove_cvref_t
<typename
_Alloc::value_type
>,
582 struct __is_alloc_insertable_impl
586 template<typename _Alloc
, typename _Tp
, typename _ValueT
>
587 struct __is_alloc_insertable_impl
<_Alloc
, _Tp
, _ValueT
,
588 __void_t
<decltype(allocator_traits
<_Alloc
>::construct(
589 std::declval
<_Alloc
&>(), std::declval
<_ValueT
*>(),
590 std::declval
<_Tp
>()))>>
594 // true if _Alloc::value_type is CopyInsertable into containers using _Alloc
595 // (might be wrong if _Alloc::construct exists but is not constrained,
596 // i.e. actually trying to use it would still be invalid. Use with caution.)
597 template<typename _Alloc
>
598 struct __is_copy_insertable
599 : __is_alloc_insertable_impl
<_Alloc
,
600 typename
_Alloc::value_type
const&>::type
603 // std::allocator<_Tp> just requires CopyConstructible
604 template<typename _Tp
>
605 struct __is_copy_insertable
<allocator
<_Tp
>>
606 : is_copy_constructible
<_Tp
>
609 // true if _Alloc::value_type is MoveInsertable into containers using _Alloc
610 // (might be wrong if _Alloc::construct exists but is not constrained,
611 // i.e. actually trying to use it would still be invalid. Use with caution.)
612 template<typename _Alloc
>
613 struct __is_move_insertable
614 : __is_alloc_insertable_impl
<_Alloc
, typename
_Alloc::value_type
>::type
617 // std::allocator<_Tp> just requires MoveConstructible
618 template<typename _Tp
>
619 struct __is_move_insertable
<allocator
<_Tp
>>
620 : is_move_constructible
<_Tp
>
623 // Trait to detect Allocator-like types.
624 template<typename _Alloc
, typename
= void>
625 struct __is_allocator
: false_type
{ };
627 template<typename _Alloc
>
628 struct __is_allocator
<_Alloc
,
629 __void_t
<typename
_Alloc::value_type
,
630 decltype(std::declval
<_Alloc
&>().allocate(size_t{}))>>
633 template<typename _Alloc
>
634 using _RequireAllocator
635 = typename enable_if
<__is_allocator
<_Alloc
>::value
, _Alloc
>::type
;
637 template<typename _Alloc
>
638 using _RequireNotAllocator
639 = typename enable_if
<!__is_allocator
<_Alloc
>::value
, _Alloc
>::type
;
641 _GLIBCXX_END_NAMESPACE_VERSION
644 #endif // _ALLOC_TRAITS_H