libstdc++-v3/include/ext/malloc_allocator.h

   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 <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