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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___CXX03___MEMORY_ALLOCATOR_H
11#define _LIBCPP___CXX03___MEMORY_ALLOCATOR_H
12
13#include <__cxx03/__config>
14#include <__cxx03/__memory/addressof.h>
15#include <__cxx03/__memory/allocate_at_least.h>
16#include <__cxx03/__memory/allocator_traits.h>
17#include <__cxx03/__type_traits/is_const.h>
18#include <__cxx03/__type_traits/is_constant_evaluated.h>
19#include <__cxx03/__type_traits/is_same.h>
20#include <__cxx03/__type_traits/is_void.h>
21#include <__cxx03/__type_traits/is_volatile.h>
22#include <__cxx03/__utility/forward.h>
23#include <__cxx03/cstddef>
24#include <__cxx03/new>
25
26#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27# pragma GCC system_header
28#endif
29
30_LIBCPP_BEGIN_NAMESPACE_STD
31
32template <class _Tp>
33class allocator;
34
35template <>
36class _LIBCPP_TEMPLATE_VIS allocator<void> {
37public:
38 typedef void* pointer;
39 typedef const void* const_pointer;
40 typedef void value_type;
41
42 template <class _Up>
43 struct rebind {
44 typedef allocator<_Up> other;
45 };
46};
47
48// TODO(LLVM 20): Remove the escape hatch
49#ifdef _LIBCPP_ENABLE_REMOVED_ALLOCATOR_CONST
50template <>
51class _LIBCPP_TEMPLATE_VIS allocator<const void> {
52public:
53 typedef const void* pointer;
54 typedef const void* const_pointer;
55 typedef const void value_type;
56
57 template <class _Up>
58 struct rebind {
59 typedef allocator<_Up> other;
60 };
61};
62#endif // _LIBCPP_ENABLE_REMOVED_ALLOCATOR_CONST
63
64// This class provides a non-trivial default constructor to the class that derives from it
65// if the condition is satisfied.
66//
67// The second template parameter exists to allow giving a unique type to __non_trivial_if,
68// which makes it possible to avoid breaking the ABI when making this a base class of an
69// existing class. Without that, imagine we have classes D1 and D2, both of which used to
70// have no base classes, but which now derive from __non_trivial_if. The layout of a class
71// that inherits from both D1 and D2 will change because the two __non_trivial_if base
72// classes are not allowed to share the same address.
73//
74// By making those __non_trivial_if base classes unique, we work around this problem and
75// it is safe to start deriving from __non_trivial_if in existing classes.
76template <bool _Cond, class _Unique>
77struct __non_trivial_if {};
78
79template <class _Unique>
80struct __non_trivial_if<true, _Unique> {
81 _LIBCPP_HIDE_FROM_ABI __non_trivial_if() _NOEXCEPT {}
82};
83
84// allocator
85//
86// Note: For ABI compatibility between C++20 and previous standards, we make
87// allocator<void> trivial in C++20.
88
89template <class _Tp>
90class _LIBCPP_TEMPLATE_VIS allocator : private __non_trivial_if<!is_void<_Tp>::value, allocator<_Tp> > {
91 static_assert(!is_const<_Tp>::value, "std::allocator does not support const types");
92 static_assert(!is_volatile<_Tp>::value, "std::allocator does not support volatile types");
93
94public:
95 typedef size_t size_type;
96 typedef ptrdiff_t difference_type;
97 typedef _Tp value_type;
98 typedef true_type propagate_on_container_move_assignment;
99 typedef true_type is_always_equal;
100
101 _LIBCPP_HIDE_FROM_ABI allocator() _NOEXCEPT = default;
102
103 template <class _Up>
104 _LIBCPP_HIDE_FROM_ABI allocator(const allocator<_Up>&) _NOEXCEPT {}
105
106 _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _Tp* allocate(size_t __n) {
107 if (__n > allocator_traits<allocator>::max_size(*this))
108 __throw_bad_array_new_length();
109 if (__libcpp_is_constant_evaluated()) {
110 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
111 } else {
112 return static_cast<_Tp*>(std::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
113 }
114 }
115
116 _LIBCPP_HIDE_FROM_ABI void deallocate(_Tp* __p, size_t __n) _NOEXCEPT {
117 if (__libcpp_is_constant_evaluated()) {
118 ::operator delete(__p);
119 } else {
120 std::__libcpp_deallocate((void*)__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
121 }
122 }
123
124 // C++20 Removed members
125 typedef _Tp* pointer;
126 typedef const _Tp* const_pointer;
127 typedef _Tp& reference;
128 typedef const _Tp& const_reference;
129
130 template <class _Up>
131 struct rebind {
132 typedef allocator<_Up> other;
133 };
134
135 _LIBCPP_HIDE_FROM_ABI pointer address(reference __x) const _NOEXCEPT { return std::addressof(__x); }
136 _LIBCPP_HIDE_FROM_ABI const_pointer address(const_reference __x) const _NOEXCEPT { return std::addressof(__x); }
137
138 _LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _Tp* allocate(size_t __n, const void*) { return allocate(__n); }
139
140 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return size_type(~0) / sizeof(_Tp); }
141
142 template <class _Up, class... _Args>
143 _LIBCPP_HIDE_FROM_ABI void construct(_Up* __p, _Args&&... __args) {
144 ::new ((void*)__p) _Up(std::forward<_Args>(__args)...);
145 }
146
147 _LIBCPP_HIDE_FROM_ABI void destroy(pointer __p) { __p->~_Tp(); }
148};
149
150template <class _Tp, class _Up>
151inline _LIBCPP_HIDE_FROM_ABI bool operator==(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {
152 return true;
153}
154
155template <class _Tp, class _Up>
156inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {
157 return false;
158}
159
160_LIBCPP_END_NAMESPACE_STD
161
162#endif // _LIBCPP___CXX03___MEMORY_ALLOCATOR_H
163

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source code of libcxx/include/__cxx03/__memory/allocator.h