1 // Allocator that wraps "C" malloc -*- 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 ext/malloc_allocator.h
26 * This file is a GNU extension to the Standard C++ Library.
27 */
28
29 #ifndef _MALLOC_ALLOCATOR_H
30 #define _MALLOC_ALLOCATOR_H 1
31
32 #include <cstdlib>
33 #include <cstddef>
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 __gnu_cxx _GLIBCXX_VISIBILITY(default)
42 {
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @brief An allocator that uses malloc.
47 * @ingroup allocators
48 *
49 * This is precisely the allocator defined in the C++ Standard.
50 * - all allocation calls malloc
51 * - all deallocation calls free
52 */
53 template<typename _Tp>
54 class malloc_allocator
55 {
56 public:
57 typedef _Tp value_type;
58 typedef std::size_t size_type;
59 typedef std::ptrdiff_t difference_type;
60 #if __cplusplus <= 201703L
61 typedef _Tp* pointer;
62 typedef const _Tp* const_pointer;
63 typedef _Tp& reference;
64 typedef const _Tp& const_reference;
65
66 template<typename _Tp1>
67 struct rebind
68 { typedef malloc_allocator<_Tp1> other; };
69 #endif
70
71 #if __cplusplus >= 201103L
72 // _GLIBCXX_RESOLVE_LIB_DEFECTS
73 // 2103. propagate_on_container_move_assignment
74 typedef std::true_type propagate_on_container_move_assignment;
75 #endif
76
77 _GLIBCXX20_CONSTEXPR
78 malloc_allocator() _GLIBCXX_USE_NOEXCEPT { }
79
80 _GLIBCXX20_CONSTEXPR
81 malloc_allocator(const malloc_allocator&) _GLIBCXX_USE_NOEXCEPT { }
82
83 template<typename _Tp1>
84 _GLIBCXX20_CONSTEXPR
85 malloc_allocator(const malloc_allocator<_Tp1>&)
86 _GLIBCXX_USE_NOEXCEPT { }
87
88 #if __cplusplus <= 201703L
89 ~malloc_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* = 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 _Tp* __ret = 0;
121 #if __cpp_aligned_new
122 #if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
123 if (alignof(_Tp) > alignof(std::max_align_t))
124 {
125 __ret = static_cast<_Tp*>(::aligned_alloc(alignof(_Tp),
126 __n * sizeof(_Tp)));
127 }
128 #else
129 # define _GLIBCXX_CHECK_MALLOC_RESULT
130 #endif
131 #endif
132 if (!__ret)
133 __ret = static_cast<_Tp*>(std::malloc(__n * sizeof(_Tp)));
134 if (!__ret)
135 std::__throw_bad_alloc();
136 #ifdef _GLIBCXX_CHECK_MALLOC_RESULT
137 #undef _GLIBCXX_CHECK_MALLOC_RESULT
138 if (reinterpret_cast<std::size_t>(__ret) % alignof(_Tp))
139 {
140 // Memory returned by malloc is not suitably aligned for _Tp.
141 deallocate(__ret, __n);
142 std::__throw_bad_alloc();
143 }
144 #endif
145 return __ret;
146 }
147
148 // __p is not permitted to be a null pointer.
149 void
150 deallocate(_Tp* __p, size_type)
151 { std::free(static_cast<void*>(__p)); }
152
153 #if __cplusplus <= 201703L
154 size_type
155 max_size() const _GLIBCXX_USE_NOEXCEPT
156 { return _M_max_size(); }
157
158 #if __cplusplus >= 201103L
159 template<typename _Up, typename... _Args>
160 void
161 construct(_Up* __p, _Args&&... __args)
162 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
163 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
164
165 template<typename _Up>
166 void
167 destroy(_Up* __p)
168 noexcept(std::is_nothrow_destructible<_Up>::value)
169 { __p->~_Up(); }
170 #else
171 // _GLIBCXX_RESOLVE_LIB_DEFECTS
172 // 402. wrong new expression in [some_] allocator::construct
173 void
174 construct(pointer __p, const _Tp& __val)
175 { ::new((void *)__p) value_type(__val); }
176
177 void
178 destroy(pointer __p) { __p->~_Tp(); }
179 #endif
180 #endif // ! C++20
181
182 template<typename _Up>
183 friend _GLIBCXX20_CONSTEXPR bool
184 operator==(const malloc_allocator&, const malloc_allocator<_Up>&)
185 _GLIBCXX_NOTHROW
186 { return true; }
187
188 #if __cpp_impl_three_way_comparison < 201907L
189 template<typename _Up>
190 friend _GLIBCXX20_CONSTEXPR bool
191 operator!=(const malloc_allocator&, const malloc_allocator<_Up>&)
192 _GLIBCXX_NOTHROW
193 { return false; }
194 #endif
195
196 private:
197 _GLIBCXX_CONSTEXPR size_type
198 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
199 {
200 #if __PTRDIFF_MAX__ < __SIZE_MAX__
201 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
202 #else
203 return std::size_t(-1) / sizeof(_Tp);
204 #endif
205 }
206 };
207
208 _GLIBCXX_END_NAMESPACE_VERSION
209 } // namespace
210
211 #endif
212