1// Allocator that wraps operator new -*- C++ -*-
2
3// Copyright (C) 2001-2024 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 * This is the default base-class implementation of `std::allocator`,
54 * and is also the base-class of the `__gnu_cxx::new_allocator` extension.
55 * You should use either `std::allocator` or `__gnu_cxx::new_allocator`
56 * instead of using this directly.
57 *
58 * @tparam _Tp Type of allocated object.
59 *
60 * @headerfile memory
61 */
62 template<typename _Tp>
63 class __new_allocator
64 {
65 public:
66 typedef _Tp value_type;
67 typedef std::size_t size_type;
68 typedef std::ptrdiff_t difference_type;
69#if __cplusplus <= 201703L
70 typedef _Tp* pointer;
71 typedef const _Tp* const_pointer;
72 typedef _Tp& reference;
73 typedef const _Tp& const_reference;
74
75 template<typename _Tp1>
76 struct rebind
77 { typedef __new_allocator<_Tp1> other; };
78#endif
79
80#if __cplusplus >= 201103L
81 // _GLIBCXX_RESOLVE_LIB_DEFECTS
82 // 2103. propagate_on_container_move_assignment
83 typedef std::true_type propagate_on_container_move_assignment;
84#endif
85
86 __attribute__((__always_inline__))
87 _GLIBCXX20_CONSTEXPR
88 __new_allocator() _GLIBCXX_USE_NOEXCEPT { }
89
90 __attribute__((__always_inline__))
91 _GLIBCXX20_CONSTEXPR
92 __new_allocator(const __new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
93
94 template<typename _Tp1>
95 __attribute__((__always_inline__))
96 _GLIBCXX20_CONSTEXPR
97 __new_allocator(const __new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
98
99#if __cplusplus >= 201103L
100 __new_allocator& operator=(const __new_allocator&) = default;
101#endif
102
103#if __cplusplus <= 201703L
104 ~__new_allocator() _GLIBCXX_USE_NOEXCEPT { }
105
106 pointer
107 address(reference __x) const _GLIBCXX_NOEXCEPT
108 { return std::__addressof(__x); }
109
110 const_pointer
111 address(const_reference __x) const _GLIBCXX_NOEXCEPT
112 { return std::__addressof(__x); }
113#endif
114
115#if __has_builtin(__builtin_operator_new) >= 201802L
116# define _GLIBCXX_OPERATOR_NEW __builtin_operator_new
117# define _GLIBCXX_OPERATOR_DELETE __builtin_operator_delete
118#else
119# define _GLIBCXX_OPERATOR_NEW ::operator new
120# define _GLIBCXX_OPERATOR_DELETE ::operator delete
121#endif
122
123 // NB: __n is permitted to be 0. The C++ standard says nothing
124 // about what the return value is when __n == 0.
125 _GLIBCXX_NODISCARD _Tp*
126 allocate(size_type __n, const void* = static_cast<const void*>(0))
127 {
128#if __cplusplus >= 201103L
129 // _GLIBCXX_RESOLVE_LIB_DEFECTS
130 // 3308. std::allocator<void>().allocate(n)
131 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
132#endif
133
134 if (__builtin_expect(__n > this->_M_max_size(), false))
135 {
136 // _GLIBCXX_RESOLVE_LIB_DEFECTS
137 // 3190. allocator::allocate sometimes returns too little storage
138 if (__n > (std::size_t(-1) / sizeof(_Tp)))
139 std::__throw_bad_array_new_length();
140 std::__throw_bad_alloc();
141 }
142
143#if __cpp_aligned_new
144 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
145 {
146 std::align_val_t __al = std::align_val_t(alignof(_Tp));
147 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp),
148 __al));
149 }
150#endif
151 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp)));
152 }
153
154 // __p is not permitted to be a null pointer.
155 void
156 deallocate(_Tp* __p, size_type __n __attribute__ ((__unused__)))
157 {
158#if __cpp_sized_deallocation
159# define _GLIBCXX_SIZED_DEALLOC(p, n) (p), (n) * sizeof(_Tp)
160#else
161# define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
162#endif
163
164#if __cpp_aligned_new
165 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
166 {
167 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),
168 std::align_val_t(alignof(_Tp)));
169 return;
170 }
171#endif
172 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
173 }
174
175#undef _GLIBCXX_SIZED_DEALLOC
176#undef _GLIBCXX_OPERATOR_DELETE
177#undef _GLIBCXX_OPERATOR_NEW
178
179#if __cplusplus <= 201703L
180 __attribute__((__always_inline__))
181 size_type
182 max_size() const _GLIBCXX_USE_NOEXCEPT
183 { return _M_max_size(); }
184
185#if __cplusplus >= 201103L
186 template<typename _Up, typename... _Args>
187 __attribute__((__always_inline__))
188 void
189 construct(_Up* __p, _Args&&... __args)
190 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
191 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
192
193 template<typename _Up>
194 __attribute__((__always_inline__))
195 void
196 destroy(_Up* __p)
197 noexcept(std::is_nothrow_destructible<_Up>::value)
198 { __p->~_Up(); }
199#else
200 // _GLIBCXX_RESOLVE_LIB_DEFECTS
201 // 402. wrong new expression in [some_] allocator::construct
202 __attribute__((__always_inline__))
203 void
204 construct(pointer __p, const _Tp& __val)
205 { ::new((void *)__p) _Tp(__val); }
206
207 __attribute__((__always_inline__))
208 void
209 destroy(pointer __p) { __p->~_Tp(); }
210#endif
211#endif // ! C++20
212
213 template<typename _Up>
214 friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR bool
215 operator==(const __new_allocator&, const __new_allocator<_Up>&)
216 _GLIBCXX_NOTHROW
217 { return true; }
218
219#if __cpp_impl_three_way_comparison < 201907L
220 template<typename _Up>
221 friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR bool
222 operator!=(const __new_allocator&, const __new_allocator<_Up>&)
223 _GLIBCXX_NOTHROW
224 { return false; }
225#endif
226
227 private:
228 __attribute__((__always_inline__))
229 _GLIBCXX_CONSTEXPR size_type
230 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
231 {
232#if __PTRDIFF_MAX__ < __SIZE_MAX__
233 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
234#else
235 return std::size_t(-1) / sizeof(_Tp);
236#endif
237 }
238 };
239
240_GLIBCXX_END_NAMESPACE_VERSION
241} // namespace
242
243#endif
244