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

   1 // Allocator that wraps "C" malloc -*- C++ -*-
   2
   3 // Copyright (C) 2001-2018 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
  41 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  42 {
  43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  44
  45   using std::size_t;
  46   using std::ptrdiff_t;
  47
  48   /**
  49    *  @brief  An allocator that uses malloc.
  50    *  @ingroup allocators
  51    *
  52    *  This is precisely the allocator defined in the C++ Standard.
  53    *    - all allocation calls malloc
  54    *    - all deallocation calls free
  55    */
  56   template<typename _Tp>
  57     class malloc_allocator
  58     {
  59     public:
  60       typedef size_t     size_type;
  61       typedef ptrdiff_t  difference_type;
  62       typedef _Tp*       pointer;
  63       typedef const _Tp* const_pointer;
  64       typedef _Tp&       reference;
  65       typedef const _Tp& const_reference;
  66       typedef _Tp        value_type;
  67
  68       template<typename _Tp1>
  69         struct rebind
  70         { typedef malloc_allocator<_Tp1> other; };
  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       malloc_allocator() _GLIBCXX_USE_NOEXCEPT { }
  80
  81       _GLIBCXX20_CONSTEXPR
  82       malloc_allocator(const malloc_allocator&) _GLIBCXX_USE_NOEXCEPT { }
  83
  84       template<typename _Tp1>
  85         _GLIBCXX20_CONSTEXPR
  86         malloc_allocator(const malloc_allocator<_Tp1>&)
  87         _GLIBCXX_USE_NOEXCEPT { }
  88
  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
  99       // NB: __n is permitted to be 0.  The C++ standard says nothing
 100       // about what the return value is when __n == 0.
 101       pointer
 102       allocate(size_type __n, const void* = 0)
 103       {
 104         if (__n > this->max_size())
 105           std::__throw_bad_alloc();
 106
 107         pointer __ret = 0;
 108 #if __cpp_aligned_new
 109 #if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
 110         if (alignof(_Tp) > alignof(std::max_align_t))
 111           {
 112             __ret = static_cast<_Tp*>(::aligned_alloc(alignof(_Tp),
 113                                                       __n * sizeof(_Tp)));
 114           }
 115 #else
 116 # define _GLIBCXX_CHECK_MALLOC_RESULT
 117 #endif
 118 #endif
 119         if (!__ret)
 120           __ret = static_cast<_Tp*>(std::malloc(__n * sizeof(_Tp)));
 121         if (!__ret)
 122           std::__throw_bad_alloc();
 123 #ifdef _GLIBCXX_CHECK_MALLOC_RESULT
 124 #undef _GLIBCXX_CHECK_MALLOC_RESULT
 125           if (reinterpret_cast<std::size_t>(__ret) % alignof(_Tp))
 126             {
 127               // Memory returned by malloc is not suitably aligned for _Tp.
 128               deallocate(__ret, __n);
 129               std::__throw_bad_alloc();
 130             }
 131 #endif
 132         return __ret;
 133       }
 134
 135       // __p is not permitted to be a null pointer.
 136       void
 137       deallocate(pointer __p, size_type)
 138       { std::free(static_cast<void*>(__p)); }
 139
 140       size_type
 141       max_size() const _GLIBCXX_USE_NOEXCEPT
 142       {
 143 #if __PTRDIFF_MAX__ < __SIZE_MAX__
 144         return size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
 145 #else
 146         return size_t(-1) / sizeof(_Tp);
 147 #endif
 148       }
 149
 150 #if __cplusplus >= 201103L
 151       template<typename _Up, typename... _Args>
 152         void
 153         construct(_Up* __p, _Args&&... __args)
 154         noexcept(noexcept(::new((void *)__p)
 155                           _Up(std::forward<_Args>(__args)...)))
 156         { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 157
 158       template<typename _Up>
 159         void
 160         destroy(_Up* __p)
 161         noexcept(noexcept(__p->~_Up()))
 162         { __p->~_Up(); }
 163 #else
 164       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 165       // 402. wrong new expression in [some_] allocator::construct
 166       void
 167       construct(pointer __p, const _Tp& __val)
 168       { ::new((void *)__p) value_type(__val); }
 169
 170       void
 171       destroy(pointer __p) { __p->~_Tp(); }
 172 #endif
 173
 174       template<typename _Up>
 175         friend bool
 176         operator==(const malloc_allocator&, const malloc_allocator<_Up>&)
 177         _GLIBCXX_NOTHROW
 178         { return true; }
 179
 180       template<typename _Up>
 181         friend bool
 182         operator!=(const malloc_allocator&, const malloc_allocator<_Up>&)
 183         _GLIBCXX_NOTHROW
 184         { return false; }
 185     };
 186
 187 _GLIBCXX_END_NAMESPACE_VERSION
 188 } // namespace
 189
 190 #endif