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1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___MEMORY_ALLOCATOR_H
11#define _LIBCPP___MEMORY_ALLOCATOR_H
12
13#include <__config>
14#include <__cstddef/ptrdiff_t.h>
15#include <__cstddef/size_t.h>
16#include <__memory/addressof.h>
17#include <__memory/allocate_at_least.h>
18#include <__memory/allocator_traits.h>
19#include <__new/allocate.h>
20#include <__new/exceptions.h>
21#include <__type_traits/is_const.h>
22#include <__type_traits/is_constant_evaluated.h>
23#include <__type_traits/is_same.h>
24#include <__type_traits/is_void.h>
25#include <__type_traits/is_volatile.h>
26#include <__utility/forward.h>
27
28#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
29# pragma GCC system_header
30#endif
31
32_LIBCPP_BEGIN_NAMESPACE_STD
33
34template <class _Tp>
35class allocator;
36
37#if _LIBCPP_STD_VER <= 17
38// These specializations shouldn't be marked _LIBCPP_DEPRECATED_IN_CXX17.
39// Specializing allocator<void> is deprecated, but not using it.
40template <>
41class allocator<void> {
42public:
43 _LIBCPP_DEPRECATED_IN_CXX17 typedef void* pointer;
44 _LIBCPP_DEPRECATED_IN_CXX17 typedef const void* const_pointer;
45 _LIBCPP_DEPRECATED_IN_CXX17 typedef void value_type;
46
47 template <class _Up>
48 struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
49 typedef allocator<_Up> other;
50 };
51};
52#endif // _LIBCPP_STD_VER <= 17
53
54// This class provides a non-trivial default constructor to the class that derives from it
55// if the condition is satisfied.
56//
57// The second template parameter exists to allow giving a unique type to __non_trivial_if,
58// which makes it possible to avoid breaking the ABI when making this a base class of an
59// existing class. Without that, imagine we have classes D1 and D2, both of which used to
60// have no base classes, but which now derive from __non_trivial_if. The layout of a class
61// that inherits from both D1 and D2 will change because the two __non_trivial_if base
62// classes are not allowed to share the same address.
63//
64// By making those __non_trivial_if base classes unique, we work around this problem and
65// it is safe to start deriving from __non_trivial_if in existing classes.
66template <bool _Cond, class _Unique>
67struct __non_trivial_if {};
68
69template <class _Unique>
70struct __non_trivial_if<true, _Unique> {
71 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __non_trivial_if() _NOEXCEPT {}
72};
73
74// allocator
75//
76// Note: For ABI compatibility between C++20 and previous standards, we make
77// allocator<void> trivial in C++20.
78
79template <class _Tp>
80class allocator : private __non_trivial_if<!is_void<_Tp>::value, allocator<_Tp> > {
81 static_assert(!is_const<_Tp>::value, "std::allocator does not support const types");
82 static_assert(!is_volatile<_Tp>::value, "std::allocator does not support volatile types");
83
84public:
85 typedef size_t size_type;
86 typedef ptrdiff_t difference_type;
87 typedef _Tp value_type;
88 typedef true_type propagate_on_container_move_assignment;
89#if _LIBCPP_STD_VER <= 23 || defined(_LIBCPP_ENABLE_CXX26_REMOVED_ALLOCATOR_MEMBERS)
90 _LIBCPP_DEPRECATED_IN_CXX23 typedef true_type is_always_equal;
91#endif
92
93 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 allocator() _NOEXCEPT = default;
94
95 template <class _Up>
96 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 allocator(const allocator<_Up>&) _NOEXCEPT {}
97
98 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp* allocate(size_t __n) {
99 static_assert(sizeof(_Tp) >= 0, "cannot allocate memory for an incomplete type");
100 if (__n > allocator_traits<allocator>::max_size(*this))
101 std::__throw_bad_array_new_length();
102 if (__libcpp_is_constant_evaluated()) {
103 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
104 } else {
105 return std::__libcpp_allocate<_Tp>(__element_count(__n));
106 }
107 }
108
109#if _LIBCPP_STD_VER >= 23
110 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr allocation_result<_Tp*> allocate_at_least(size_t __n) {
111 static_assert(sizeof(_Tp) >= 0, "cannot allocate memory for an incomplete type");
112 return {allocate(__n), __n};
113 }
114#endif
115
116 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void deallocate(_Tp* __p, size_t __n) _NOEXCEPT {
117 if (__libcpp_is_constant_evaluated()) {
118 ::operator delete(__p);
119 } else {
120 std::__libcpp_deallocate<_Tp>(__p, __element_count(__n));
121 }
122 }
123
124 // C++20 Removed members
125#if _LIBCPP_STD_VER <= 17
126 _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp* pointer;
127 _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* const_pointer;
128 _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp& reference;
129 _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& const_reference;
130
131 template <class _Up>
132 struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
133 typedef allocator<_Up> other;
134 };
135
136 _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI pointer address(reference __x) const _NOEXCEPT {
137 return std::addressof(__x);
138 }
139 _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI const_pointer address(const_reference __x) const _NOEXCEPT {
140 return std::addressof(__x);
141 }
142
143 [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_DEPRECATED_IN_CXX17 _Tp* allocate(size_t __n, const void*) {
144 return allocate(__n);
145 }
146
147 _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
148 return size_type(~0) / sizeof(_Tp);
149 }
150
151 template <class _Up, class... _Args>
152 _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI void construct(_Up* __p, _Args&&... __args) {
153 ::new ((void*)__p) _Up(std::forward<_Args>(__args)...);
154 }
155
156 _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI void destroy(pointer __p) { __p->~_Tp(); }
157#endif
158};
159
160template <class _Tp, class _Up>
161inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
162operator==(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {
163 return true;
164}
165
166#if _LIBCPP_STD_VER <= 17
167
168template <class _Tp, class _Up>
169inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {
170 return false;
171}
172
173#endif
174
175_LIBCPP_END_NAMESPACE_STD
176
177#endif // _LIBCPP___MEMORY_ALLOCATOR_H