1// Allocator that wraps operator new -*- C++ -*-
2
3// Copyright (C) 2001-2021 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 ext/new_allocator.h
26 * This file is a GNU extension to the Standard C++ Library.
27 */
28
29#ifndef _NEW_ALLOCATOR_H
30#define _NEW_ALLOCATOR_H 1
31
32#include <bits/c++config.h>
33#include <new>
34#include <bits/functexcept.h>
35#include <bits/move.h>
36#if __cplusplus >= 201103L
37#include <type_traits>
38#endif
39
40namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
41{
42_GLIBCXX_BEGIN_NAMESPACE_VERSION
43
44 /**
45 * @brief An allocator that uses global new, as per C++03 [20.4.1].
46 * @ingroup allocators
47 *
48 * This is precisely the allocator defined in the C++ Standard.
49 * - all allocation calls operator new
50 * - all deallocation calls operator delete
51 *
52 * @tparam _Tp Type of allocated object.
53 */
54 template<typename _Tp>
55 class new_allocator
56 {
57 public:
58 typedef _Tp value_type;
59 typedef std::size_t size_type;
60 typedef std::ptrdiff_t difference_type;
61#if __cplusplus <= 201703L
62 typedef _Tp* pointer;
63 typedef const _Tp* const_pointer;
64 typedef _Tp& reference;
65 typedef const _Tp& const_reference;
66
67 template<typename _Tp1>
68 struct rebind
69 { typedef new_allocator<_Tp1> other; };
70#endif
71
72#if __cplusplus >= 201103L
73 // _GLIBCXX_RESOLVE_LIB_DEFECTS
74 // 2103. propagate_on_container_move_assignment
75 typedef std::true_type propagate_on_container_move_assignment;
76#endif
77
78 _GLIBCXX20_CONSTEXPR
79 new_allocator() _GLIBCXX_USE_NOEXCEPT { }
80
81 _GLIBCXX20_CONSTEXPR
82 new_allocator(const new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
83
84 template<typename _Tp1>
85 _GLIBCXX20_CONSTEXPR
86 new_allocator(const new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
87
88#if __cplusplus <= 201703L
89 ~new_allocator() _GLIBCXX_USE_NOEXCEPT { }
90
91 pointer
92 address(reference __x) const _GLIBCXX_NOEXCEPT
93 { return std::__addressof(__x); }
94
95 const_pointer
96 address(const_reference __x) const _GLIBCXX_NOEXCEPT
97 { return std::__addressof(__x); }
98#endif
99
100 // NB: __n is permitted to be 0. The C++ standard says nothing
101 // about what the return value is when __n == 0.
102 _GLIBCXX_NODISCARD _Tp*
103 allocate(size_type __n, const void* = static_cast<const void*>(0))
104 {
105#if __cplusplus >= 201103L
106 // _GLIBCXX_RESOLVE_LIB_DEFECTS
107 // 3308. std::allocator<void>().allocate(n)
108 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
109#endif
110
111 if (__builtin_expect(__n > this->_M_max_size(), false))
112 {
113 // _GLIBCXX_RESOLVE_LIB_DEFECTS
114 // 3190. allocator::allocate sometimes returns too little storage
115 if (__n > (std::size_t(-1) / sizeof(_Tp)))
116 std::__throw_bad_array_new_length();
117 std::__throw_bad_alloc();
118 }
119
120#if __cpp_aligned_new
121 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
122 {
123 std::align_val_t __al = std::align_val_t(alignof(_Tp));
124 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al));
125 }
126#endif
127 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
128 }
129
130 // __p is not permitted to be a null pointer.
131 void
132 deallocate(_Tp* __p, size_type __t __attribute__ ((__unused__)))
133 {
134#if __cpp_aligned_new
135 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
136 {
137 ::operator delete(__p,
138# if __cpp_sized_deallocation
139 __t * sizeof(_Tp),
140# endif
141 std::align_val_t(alignof(_Tp)));
142 return;
143 }
144#endif
145 ::operator delete(__p
146#if __cpp_sized_deallocation
147 , __t * sizeof(_Tp)
148#endif
149 );
150 }
151
152#if __cplusplus <= 201703L
153 size_type
154 max_size() const _GLIBCXX_USE_NOEXCEPT
155 { return _M_max_size(); }
156
157#if __cplusplus >= 201103L
158 template<typename _Up, typename... _Args>
159 void
160 construct(_Up* __p, _Args&&... __args)
161 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
162 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
163
164 template<typename _Up>
165 void
166 destroy(_Up* __p)
167 noexcept(std::is_nothrow_destructible<_Up>::value)
168 { __p->~_Up(); }
169#else
170 // _GLIBCXX_RESOLVE_LIB_DEFECTS
171 // 402. wrong new expression in [some_] allocator::construct
172 void
173 construct(pointer __p, const _Tp& __val)
174 { ::new((void *)__p) _Tp(__val); }
175
176 void
177 destroy(pointer __p) { __p->~_Tp(); }
178#endif
179#endif // ! C++20
180
181 template<typename _Up>
182 friend _GLIBCXX20_CONSTEXPR bool
183 operator==(const new_allocator&, const new_allocator<_Up>&)
184 _GLIBCXX_NOTHROW
185 { return true; }
186
187#if __cpp_impl_three_way_comparison < 201907L
188 template<typename _Up>
189 friend _GLIBCXX20_CONSTEXPR bool
190 operator!=(const new_allocator&, const new_allocator<_Up>&)
191 _GLIBCXX_NOTHROW
192 { return false; }
193#endif
194
195 private:
196 _GLIBCXX_CONSTEXPR size_type
197 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
198 {
199#if __PTRDIFF_MAX__ < __SIZE_MAX__
200 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
201#else
202 return std::size_t(-1) / sizeof(_Tp);
203#endif
204 }
205 };
206
207_GLIBCXX_END_NAMESPACE_VERSION
208} // namespace
209
210#endif
211

source code of include/c++/11/ext/new_allocator.h