1 // Allocator that wraps operator new -*- C++ -*-
2
3 // Copyright (C) 2001-2023 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
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 __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 <= 201703L
100 ~__new_allocator() _GLIBCXX_USE_NOEXCEPT { }
101
102 pointer
103 address(reference __x) const _GLIBCXX_NOEXCEPT
104 { return std::__addressof(__x); }
105
106 const_pointer
107 address(const_reference __x) const _GLIBCXX_NOEXCEPT
108 { return std::__addressof(__x); }
109 #endif
110
111 #if __has_builtin(__builtin_operator_new) >= 201802L
112 # define _GLIBCXX_OPERATOR_NEW __builtin_operator_new
113 # define _GLIBCXX_OPERATOR_DELETE __builtin_operator_delete
114 #else
115 # define _GLIBCXX_OPERATOR_NEW ::operator new
116 # define _GLIBCXX_OPERATOR_DELETE ::operator delete
117 #endif
118
119 // NB: __n is permitted to be 0. The C++ standard says nothing
120 // about what the return value is when __n == 0.
121 _GLIBCXX_NODISCARD _Tp*
122 allocate(size_type __n, const void* = static_cast<const void*>(0))
123 {
124 #if __cplusplus >= 201103L
125 // _GLIBCXX_RESOLVE_LIB_DEFECTS
126 // 3308. std::allocator<void>().allocate(n)
127 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
128 #endif
129
130 if (__builtin_expect(__n > this->_M_max_size(), false))
131 {
132 // _GLIBCXX_RESOLVE_LIB_DEFECTS
133 // 3190. allocator::allocate sometimes returns too little storage
134 if (__n > (std::size_t(-1) / sizeof(_Tp)))
135 std::__throw_bad_array_new_length();
136 std::__throw_bad_alloc();
137 }
138
139 #if __cpp_aligned_new
140 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
141 {
142 std::align_val_t __al = std::align_val_t(alignof(_Tp));
143 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp),
144 __al));
145 }
146 #endif
147 return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp)));
148 }
149
150 // __p is not permitted to be a null pointer.
151 void
152 deallocate(_Tp* __p, size_type __n __attribute__ ((__unused__)))
153 {
154 #if __cpp_sized_deallocation
155 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p), (n) * sizeof(_Tp)
156 #else
157 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
158 #endif
159
160 #if __cpp_aligned_new
161 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
162 {
163 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),
164 std::align_val_t(alignof(_Tp)));
165 return;
166 }
167 #endif
168 _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
169 }
170
171 #undef _GLIBCXX_SIZED_DEALLOC
172 #undef _GLIBCXX_OPERATOR_DELETE
173 #undef _GLIBCXX_OPERATOR_NEW
174
175 #if __cplusplus <= 201703L
176 __attribute__((__always_inline__))
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 __attribute__((__always_inline__))
184 void
185 construct(_Up* __p, _Args&&... __args)
186 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
187 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
188
189 template<typename _Up>
190 __attribute__((__always_inline__))
191 void
192 destroy(_Up* __p)
193 noexcept(std::is_nothrow_destructible<_Up>::value)
194 { __p->~_Up(); }
195 #else
196 // _GLIBCXX_RESOLVE_LIB_DEFECTS
197 // 402. wrong new expression in [some_] allocator::construct
198 __attribute__((__always_inline__))
199 void
200 construct(pointer __p, const _Tp& __val)
201 { ::new((void *)__p) _Tp(__val); }
202
203 __attribute__((__always_inline__))
204 void
205 destroy(pointer __p) { __p->~_Tp(); }
206 #endif
207 #endif // ! C++20
208
209 template<typename _Up>
210 friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR bool
211 operator==(const __new_allocator&, const __new_allocator<_Up>&)
212 _GLIBCXX_NOTHROW
213 { return true; }
214
215 #if __cpp_impl_three_way_comparison < 201907L
216 template<typename _Up>
217 friend __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR bool
218 operator!=(const __new_allocator&, const __new_allocator<_Up>&)
219 _GLIBCXX_NOTHROW
220 { return false; }
221 #endif
222
223 private:
224 __attribute__((__always_inline__))
225 _GLIBCXX_CONSTEXPR size_type
226 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
227 {
228 #if __PTRDIFF_MAX__ < __SIZE_MAX__
229 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
230 #else
231 return std::size_t(-1) / sizeof(_Tp);
232 #endif
233 }
234 };
235
236 _GLIBCXX_END_NAMESPACE_VERSION
237 } // namespace
238
239 #endif