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

   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
  40 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  41 {
  42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  43
  44   /**
  45    *  @brief  An allocator that uses global new, as per [20.4].
  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 (__builtin_expect(__n > this->_M_max_size(), false))
 106           {
 107             // _GLIBCXX_RESOLVE_LIB_DEFECTS
 108             // 3190. allocator::allocate sometimes returns too little storage
 109             if (__n > (std::size_t(-1) / sizeof(_Tp)))
 110               std::__throw_bad_array_new_length();
 111             std::__throw_bad_alloc();
 112           }
 113
 114 #if __cpp_aligned_new
 115         if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 116           {
 117             std::align_val_t __al = std::align_val_t(alignof(_Tp));
 118             return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al));
 119           }
 120 #endif
 121         return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
 122       }
 123
 124       // __p is not permitted to be a null pointer.
 125       void
 126       deallocate(_Tp* __p, size_type __t __attribute__ ((__unused__)))
 127       {
 128 #if __cpp_aligned_new
 129         if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 130           {
 131             ::operator delete(__p,
 132 # if __cpp_sized_deallocation
 133                               __t * sizeof(_Tp),
 134 # endif
 135                               std::align_val_t(alignof(_Tp)));
 136             return;
 137           }
 138 #endif
 139         ::operator delete(__p
 140 #if __cpp_sized_deallocation
 141                           , __t * sizeof(_Tp)
 142 #endif
 143                          );
 144       }
 145
 146 #if __cplusplus <= 201703L
 147       size_type
 148       max_size() const _GLIBCXX_USE_NOEXCEPT
 149       { return _M_max_size(); }
 150
 151 #if __cplusplus >= 201103L
 152       template<typename _Up, typename... _Args>
 153         void
 154         construct(_Up* __p, _Args&&... __args)
 155         noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
 156         { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 157
 158       template<typename _Up>
 159         void
 160         destroy(_Up* __p)
 161         noexcept(std::is_nothrow_destructible<_Up>::value)
 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) _Tp(__val); }
 169
 170       void
 171       destroy(pointer __p) { __p->~_Tp(); }
 172 #endif
 173 #endif // ! C++20
 174
 175       template<typename _Up>
 176         friend _GLIBCXX20_CONSTEXPR bool
 177         operator==(const new_allocator&, const new_allocator<_Up>&)
 178         _GLIBCXX_NOTHROW
 179         { return true; }
 180
 181 #if __cpp_impl_three_way_comparison < 201907L
 182       template<typename _Up>
 183         friend _GLIBCXX20_CONSTEXPR bool
 184         operator!=(const new_allocator&, const new_allocator<_Up>&)
 185         _GLIBCXX_NOTHROW
 186         { return false; }
 187 #endif
 188
 189     private:
 190       _GLIBCXX_CONSTEXPR size_type
 191       _M_max_size() const _GLIBCXX_USE_NOEXCEPT
 192       {
 193 #if __PTRDIFF_MAX__ < __SIZE_MAX__
 194         return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
 195 #else
 196         return std::size_t(-1) / sizeof(_Tp);
 197 #endif
 198       }
 199     };
 200
 201 _GLIBCXX_END_NAMESPACE_VERSION
 202 } // namespace
 203
 204 #endif