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
_GLIBCXX_VISIBILITY(default)41 namespace 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 _GLIBCXX20_CONSTEXPR
87 __new_allocator() _GLIBCXX_USE_NOEXCEPT { }
88
89 _GLIBCXX20_CONSTEXPR
90 __new_allocator(const __new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
91
92 template<typename _Tp1>
93 _GLIBCXX20_CONSTEXPR
94 __new_allocator(const __new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
95
96 #if __cplusplus >= 201103L
97 __new_allocator& operator=(const __new_allocator&) = default;
98 #endif
99
100 #if __cplusplus <= 201703L
101 ~__new_allocator() _GLIBCXX_USE_NOEXCEPT { }
102
103 pointer
104 address(reference __x) const _GLIBCXX_NOEXCEPT
105 { return std::__addressof(__x); }
106
107 const_pointer
108 address(const_reference __x) const _GLIBCXX_NOEXCEPT
109 { return std::__addressof(__x); }
110 #endif
111
112 #if __has_builtin(__builtin_operator_new) >= 201802L
113 # define _GLIBCXX_OPERATOR_NEW __builtin_operator_new
114 # define _GLIBCXX_OPERATOR_DELETE __builtin_operator_delete
115 #else
116 # define _GLIBCXX_OPERATOR_NEW ::operator new
117 # define _GLIBCXX_OPERATOR_DELETE ::operator delete
118 #endif
119
120 // NB: __n is permitted to be 0. The C++ standard says nothing
121 // about what the return value is when __n == 0.
122 _GLIBCXX_NODISCARD _Tp*
123 allocate(size_type __n, const void* = static_cast<const void*>(0))
124 {
125 #if __cplusplus >= 201103L
126 // _GLIBCXX_RESOLVE_LIB_DEFECTS
127 // 3308. std::allocator<void>().allocate(n)
128 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
129 #endif
130
131 if (__builtin_expect(__n > this->_M_max_size(), false))
132 {
133 // _GLIBCXX_RESOLVE_LIB_DEFECTS
134 // 3190. allocator::allocate sometimes returns too little storage
135 if (__n > (std::size_t(-1) / sizeof(_Tp)))
136 std::__throw_bad_array_new_length();
137 std::__throw_bad_alloc();
138 }
139
140 #if __cpp_aligned_new
141 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
142 {
143 std::align_val_t __al = std::align_val_t(alignof(_Tp));
144 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp),
145 __al));
146 }
147 #endif
148 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp)));
149 }
150
151 // __p is not permitted to be a null pointer.
152 void
153 deallocate(_Tp* __p, size_type __n __attribute__ ((__unused__)))
154 {
155 #if __cpp_sized_deallocation
156 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p), (n) * sizeof(_Tp)
157 #else
158 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
159 #endif
160
161 #if __cpp_aligned_new
162 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
163 {
164 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),
165 std::align_val_t(alignof(_Tp)));
166 return;
167 }
168 #endif
169 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
170 }
171
172 #undef _GLIBCXX_SIZED_DEALLOC
173 #undef _GLIBCXX_OPERATOR_DELETE
174 #undef _GLIBCXX_OPERATOR_NEW
175
176 #if __cplusplus <= 201703L
177 size_type
178 max_size() const _GLIBCXX_USE_NOEXCEPT
179 { return _M_max_size(); }
180
181 #if __cplusplus >= 201103L
182 template<typename _Up, typename... _Args>
183 void
184 construct(_Up* __p, _Args&&... __args)
185 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
186 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
187
188 template<typename _Up>
189 void
190 destroy(_Up* __p)
191 noexcept(std::is_nothrow_destructible<_Up>::value)
192 { __p->~_Up(); }
193 #else
194 // _GLIBCXX_RESOLVE_LIB_DEFECTS
195 // 402. wrong new expression in [some_] allocator::construct
196 void
197 construct(pointer __p, const _Tp& __val)
198 { ::new((void *)__p) _Tp(__val); }
199
200 void
201 destroy(pointer __p) { __p->~_Tp(); }
202 #endif
203 #endif // ! C++20
204
205 template<typename _Up>
206 friend _GLIBCXX20_CONSTEXPR bool
207 operator==(const __new_allocator&, const __new_allocator<_Up>&)
208 _GLIBCXX_NOTHROW
209 { return true; }
210
211 #if __cpp_impl_three_way_comparison < 201907L
212 template<typename _Up>
213 friend _GLIBCXX20_CONSTEXPR bool
214 operator!=(const __new_allocator&, const __new_allocator<_Up>&)
215 _GLIBCXX_NOTHROW
216 { return false; }
217 #endif
218
219 private:
220 _GLIBCXX_CONSTEXPR size_type
221 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
222 {
223 #if __PTRDIFF_MAX__ < __SIZE_MAX__
224 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
225 #else
226 return std::size_t(-1) / sizeof(_Tp);
227 #endif
228 }
229 };
230
231 _GLIBCXX_END_NAMESPACE_VERSION
232 } // namespace
233
234 #endif
235