1 // Allocator that wraps "C" malloc -*- 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 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 <bits/requires_hosted.h> // malloc
33
34 #include <cstdlib>
35 #include <cstddef>
36 #include <new>
37 #include <bits/functexcept.h>
38 #include <bits/move.h>
39 #if __cplusplus >= 201103L
40 #include <type_traits>
41 #endif
42
43 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46
47 /**
48 * @brief An allocator that uses malloc.
49 * @ingroup allocators
50 *
51 * This is precisely the allocator defined in the C++ Standard.
52 * - all allocation calls malloc
53 * - all deallocation calls free
54 */
55 template<typename _Tp>
56 class malloc_allocator
57 {
58 public:
59 typedef _Tp value_type;
60 typedef std::size_t size_type;
61 typedef std::ptrdiff_t difference_type;
62 #if __cplusplus <= 201703L
63 typedef _Tp* pointer;
64 typedef const _Tp* const_pointer;
65 typedef _Tp& reference;
66 typedef const _Tp& const_reference;
67
68 template<typename _Tp1>
69 struct rebind
70 { typedef malloc_allocator<_Tp1> other; };
71 #endif
72
73 #if __cplusplus >= 201103L
74 // _GLIBCXX_RESOLVE_LIB_DEFECTS
75 // 2103. propagate_on_container_move_assignment
76 typedef std::true_type propagate_on_container_move_assignment;
77 #endif
78
79 _GLIBCXX20_CONSTEXPR
80 malloc_allocator() _GLIBCXX_USE_NOEXCEPT { }
81
82 _GLIBCXX20_CONSTEXPR
83 malloc_allocator(const malloc_allocator&) _GLIBCXX_USE_NOEXCEPT { }
84
85 template<typename _Tp1>
86 _GLIBCXX20_CONSTEXPR
87 malloc_allocator(const malloc_allocator<_Tp1>&)
88 _GLIBCXX_USE_NOEXCEPT { }
89
90 #if __cplusplus <= 201703L
91 ~malloc_allocator() _GLIBCXX_USE_NOEXCEPT { }
92
93 pointer
94 address(reference __x) const _GLIBCXX_NOEXCEPT
95 { return std::__addressof(__x); }
96
97 const_pointer
98 address(const_reference __x) const _GLIBCXX_NOEXCEPT
99 { return std::__addressof(__x); }
100 #endif
101
102 // NB: __n is permitted to be 0. The C++ standard says nothing
103 // about what the return value is when __n == 0.
104 _GLIBCXX_NODISCARD _Tp*
105 allocate(size_type __n, const void* = 0)
106 {
107 #if __cplusplus >= 201103L
108 // _GLIBCXX_RESOLVE_LIB_DEFECTS
109 // 3308. std::allocator<void>().allocate(n)
110 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
111 #endif
112
113 if (__builtin_expect(__n > this->_M_max_size(), false))
114 {
115 // _GLIBCXX_RESOLVE_LIB_DEFECTS
116 // 3190. allocator::allocate sometimes returns too little storage
117 if (__n > (std::size_t(-1) / sizeof(_Tp)))
118 std::__throw_bad_array_new_length();
119 std::__throw_bad_alloc();
120 }
121
122 _Tp* __ret = 0;
123 #if __cpp_aligned_new
124 #if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
125 if (alignof(_Tp) > alignof(std::max_align_t))
126 {
127 __ret = static_cast<_Tp*>(::aligned_alloc(alignof(_Tp),
128 __n * sizeof(_Tp)));
129 }
130 #else
131 # define _GLIBCXX_CHECK_MALLOC_RESULT
132 #endif
133 #endif
134 if (!__ret)
135 __ret = static_cast<_Tp*>(std::malloc(__n * sizeof(_Tp)));
136 if (!__ret)
137 std::__throw_bad_alloc();
138 #ifdef _GLIBCXX_CHECK_MALLOC_RESULT
139 #undef _GLIBCXX_CHECK_MALLOC_RESULT
140 if (reinterpret_cast<std::size_t>(__ret) % alignof(_Tp))
141 {
142 // Memory returned by malloc is not suitably aligned for _Tp.
143 deallocate(__ret, __n);
144 std::__throw_bad_alloc();
145 }
146 #endif
147 return __ret;
148 }
149
150 // __p is not permitted to be a null pointer.
151 void
152 deallocate(_Tp* __p, size_type)
153 { std::free(static_cast<void*>(__p)); }
154
155 #if __cplusplus <= 201703L
156 size_type
157 max_size() const _GLIBCXX_USE_NOEXCEPT
158 { return _M_max_size(); }
159
160 #if __cplusplus >= 201103L
161 template<typename _Up, typename... _Args>
162 void
163 construct(_Up* __p, _Args&&... __args)
164 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
165 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
166
167 template<typename _Up>
168 void
169 destroy(_Up* __p)
170 noexcept(std::is_nothrow_destructible<_Up>::value)
171 { __p->~_Up(); }
172 #else
173 // _GLIBCXX_RESOLVE_LIB_DEFECTS
174 // 402. wrong new expression in [some_] allocator::construct
175 void
176 construct(pointer __p, const _Tp& __val)
177 { ::new((void *)__p) value_type(__val); }
178
179 void
180 destroy(pointer __p) { __p->~_Tp(); }
181 #endif
182 #endif // ! C++20
183
184 template<typename _Up>
185 friend _GLIBCXX20_CONSTEXPR bool
186 operator==(const malloc_allocator&, const malloc_allocator<_Up>&)
187 _GLIBCXX_NOTHROW
188 { return true; }
189
190 #if __cpp_impl_three_way_comparison < 201907L
191 template<typename _Up>
192 friend _GLIBCXX20_CONSTEXPR bool
193 operator!=(const malloc_allocator&, const malloc_allocator<_Up>&)
194 _GLIBCXX_NOTHROW
195 { return false; }
196 #endif
197
198 private:
199 _GLIBCXX_CONSTEXPR size_type
200 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
201 {
202 #if __PTRDIFF_MAX__ < __SIZE_MAX__
203 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
204 #else
205 return std::size_t(-1) / sizeof(_Tp);
206 #endif
207 }
208 };
209
210 _GLIBCXX_END_NAMESPACE_VERSION
211 } // namespace
212
213 #endif