1// Allocator that wraps operator new -*- C++ -*-
2
3// Copyright (C) 2001-2022 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/new_allocator.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 _STD_NEW_ALLOCATOR_H
31#define _STD_NEW_ALLOCATOR_H 1
32
33#include <bits/c++config.h>
34#include <new>
35#include <bits/functexcept.h>
36#include <bits/move.h>
37#if __cplusplus >= 201103L
38#include <type_traits>
39#endif
40
41namespace std _GLIBCXX_VISIBILITY(default)
42{
43_GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @brief An allocator that uses global new, as per C++03 [20.4.1].
47 * @ingroup allocators
48 *
49 * This is precisely the allocator defined in the C++ Standard.
50 * - all allocation calls operator new
51 * - all deallocation calls operator delete
52 *
53 * @tparam _Tp Type of allocated object.
54 */
55 template<typename _Tp>
56 class __new_allocator
57 {
58 public:
59 typedef _Tp value_type;
60 typedef std::size_t size_type;
61 typedef std::ptrdiff_t difference_type;
62#if __cplusplus <= 201703L
63 typedef _Tp* pointer;
64 typedef const _Tp* const_pointer;
65 typedef _Tp& reference;
66 typedef const _Tp& const_reference;
67
68 template<typename _Tp1>
69 struct rebind
70 { typedef __new_allocator<_Tp1> other; };
71#endif
72
73#if __cplusplus >= 201103L
74 // _GLIBCXX_RESOLVE_LIB_DEFECTS
75 // 2103. propagate_on_container_move_assignment
76 typedef std::true_type propagate_on_container_move_assignment;
77#endif
78
79 _GLIBCXX20_CONSTEXPR
80 __new_allocator() _GLIBCXX_USE_NOEXCEPT { }
81
82 _GLIBCXX20_CONSTEXPR
83 __new_allocator(const __new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
84
85 template<typename _Tp1>
86 _GLIBCXX20_CONSTEXPR
87 __new_allocator(const __new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
88
89#if __cplusplus <= 201703L
90 ~__new_allocator() _GLIBCXX_USE_NOEXCEPT { }
91
92 pointer
93 address(reference __x) const _GLIBCXX_NOEXCEPT
94 { return std::__addressof(__x); }
95
96 const_pointer
97 address(const_reference __x) const _GLIBCXX_NOEXCEPT
98 { return std::__addressof(__x); }
99#endif
100
101#if __has_builtin(__builtin_operator_new) >= 201802L
102# define _GLIBCXX_OPERATOR_NEW __builtin_operator_new
103# define _GLIBCXX_OPERATOR_DELETE __builtin_operator_delete
104#else
105# define _GLIBCXX_OPERATOR_NEW ::operator new
106# define _GLIBCXX_OPERATOR_DELETE ::operator delete
107#endif
108
109 // NB: __n is permitted to be 0. The C++ standard says nothing
110 // about what the return value is when __n == 0.
111 _GLIBCXX_NODISCARD _Tp*
112 allocate(size_type __n, const void* = static_cast<const void*>(0))
113 {
114#if __cplusplus >= 201103L
115 // _GLIBCXX_RESOLVE_LIB_DEFECTS
116 // 3308. std::allocator<void>().allocate(n)
117 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
118#endif
119
120 if (__builtin_expect(__n > this->_M_max_size(), false))
121 {
122 // _GLIBCXX_RESOLVE_LIB_DEFECTS
123 // 3190. allocator::allocate sometimes returns too little storage
124 if (__n > (std::size_t(-1) / sizeof(_Tp)))
125 std::__throw_bad_array_new_length();
126 std::__throw_bad_alloc();
127 }
128
129#if __cpp_aligned_new
130 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
131 {
132 std::align_val_t __al = std::align_val_t(alignof(_Tp));
133 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp),
134 __al));
135 }
136#endif
137 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp)));
138 }
139
140 // __p is not permitted to be a null pointer.
141 void
142 deallocate(_Tp* __p, size_type __n __attribute__ ((__unused__)))
143 {
144#if __cpp_sized_deallocation
145# define _GLIBCXX_SIZED_DEALLOC(p, n) (p), (n) * sizeof(_Tp)
146#else
147# define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
148#endif
149
150#if __cpp_aligned_new
151 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
152 {
153 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),
154 std::align_val_t(alignof(_Tp)));
155 return;
156 }
157#endif
158 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
159 }
160
161#undef _GLIBCXX_SIZED_DEALLOC
162#undef _GLIBCXX_OPERATOR_DELETE
163#undef _GLIBCXX_OPERATOR_NEW
164
165#if __cplusplus <= 201703L
166 size_type
167 max_size() const _GLIBCXX_USE_NOEXCEPT
168 { return _M_max_size(); }
169
170#if __cplusplus >= 201103L
171 template<typename _Up, typename... _Args>
172 void
173 construct(_Up* __p, _Args&&... __args)
174 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
175 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
176
177 template<typename _Up>
178 void
179 destroy(_Up* __p)
180 noexcept(std::is_nothrow_destructible<_Up>::value)
181 { __p->~_Up(); }
182#else
183 // _GLIBCXX_RESOLVE_LIB_DEFECTS
184 // 402. wrong new expression in [some_] allocator::construct
185 void
186 construct(pointer __p, const _Tp& __val)
187 { ::new((void *)__p) _Tp(__val); }
188
189 void
190 destroy(pointer __p) { __p->~_Tp(); }
191#endif
192#endif // ! C++20
193
194 template<typename _Up>
195 friend _GLIBCXX20_CONSTEXPR bool
196 operator==(const __new_allocator&, const __new_allocator<_Up>&)
197 _GLIBCXX_NOTHROW
198 { return true; }
199
200#if __cpp_impl_three_way_comparison < 201907L
201 template<typename _Up>
202 friend _GLIBCXX20_CONSTEXPR bool
203 operator!=(const __new_allocator&, const __new_allocator<_Up>&)
204 _GLIBCXX_NOTHROW
205 { return false; }
206#endif
207
208 private:
209 _GLIBCXX_CONSTEXPR size_type
210 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
211 {
212#if __PTRDIFF_MAX__ < __SIZE_MAX__
213 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
214#else
215 return std::size_t(-1) / sizeof(_Tp);
216#endif
217 }
218 };
219
220_GLIBCXX_END_NAMESPACE_VERSION
221} // namespace
222
223#endif
224