Allocators

Functions
namespace __gnu_cxx	_GLIBCXX_VISIBILITY (default)

Detailed Description

Classes encapsulating memory operations.

Function Documentation

namespace __gnu_cxx _GLIBCXX_VISIBILITY

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default

)

Uniform interface to C++98 and C++0x allocators.

Base class.

An allocator that uses previously allocated memory. This memory can be externally, globally, or otherwise allocated.

A meta-allocator with debugging bits, as per [20.4].

This is precisely the allocator defined in the C++ Standard.

• all allocation calls operator new
• all deallocation calls operator delete

An example allocator which uses a non-standard pointer type.

This allocator specifies that containers use a 'relative pointer' as it's pointer type. (See ext/pointer.h) Memory allocation in this example is still performed using std::allocator.

An allocator that uses malloc.

This is precisely the allocator defined in the C++ Standard.

• all allocation calls malloc
• all deallocation calls free

Base class for pool object.

Data describing the underlying memory pool, parameterized on threading support.

Specialization for single thread.

Policy for shared __pool objects.

Policy for individual __pool objects.

Base class for _Tp dependent member functions.

This is a fixed size (power of 2) allocator which - when compiled with thread support - will maintain one freelist per size per thread plus a global one. Steps are taken to limit the per thread freelist sizes (by returning excess back to the global list).

Further details: http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt12ch32.html

An allocator that uses global new, as per [20.4].

This is precisely the allocator defined in the C++ Standard.

• all allocation calls operator new
• all deallocation calls operator delete

Template Parameters

_Tp	Type of allocated object.

Base class for __pool_alloc.

Uses various allocators to fulfill underlying requests (and makes as few requests as possible when in default high-speed pool mode).

Important implementation properties: 0. If globally mandated, then allocate objects from new

1. If the clients request an object of size > _S_max_bytes, the resulting object will be obtained directly from new
2. In all other cases, we allocate an object of size exactly _S_round_up(requested_size). Thus the client has enough size information that we can return the object to the proper free list without permanently losing part of the object.

Allocator using a memory pool with a single lock.

{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

#if __cplusplus >= 201103L
  template<typename _Alloc>
    struct __allocator_always_compares_equal
    { static const bool value = false; };

  template<typename _Alloc>
    const bool __allocator_always_compares_equal<_Alloc>::value;

  template<typename _Tp>
    struct __allocator_always_compares_equal<std::allocator<_Tp>>
    { static const bool value = true; };

  template<typename _Tp>
    const bool __allocator_always_compares_equal<std::allocator<_Tp>>::value;

  template<typename, typename> struct array_allocator;

  template<typename _Tp, typename _Array>
    struct __allocator_always_compares_equal<array_allocator<_Tp, _Array>>
    { static const bool value = true; };

  template<typename _Tp, typename _Array>
    const bool
    __allocator_always_compares_equal<array_allocator<_Tp, _Array>>::value;

  template<typename> struct bitmap_allocator;

  template<typename _Tp>
    struct __allocator_always_compares_equal<bitmap_allocator<_Tp>>
    { static const bool value = true; };

  template<typename _Tp>
    const bool __allocator_always_compares_equal<bitmap_allocator<_Tp>>::value;

  template<typename> struct malloc_allocator;

  template<typename _Tp>
    struct __allocator_always_compares_equal<malloc_allocator<_Tp>>
    { static const bool value = true; };

  template<typename _Tp>
    const bool __allocator_always_compares_equal<malloc_allocator<_Tp>>::value;

  template<typename> struct mt_allocator;

  template<typename _Tp>
    struct __allocator_always_compares_equal<mt_allocator<_Tp>>
    { static const bool value = true; };

  template<typename _Tp>
    const bool __allocator_always_compares_equal<mt_allocator<_Tp>>::value;

  template<typename> struct new_allocator;

  template<typename _Tp>
    struct __allocator_always_compares_equal<new_allocator<_Tp>>
    { static const bool value = true; };

  template<typename _Tp>
    const bool __allocator_always_compares_equal<new_allocator<_Tp>>::value;

  template<typename> struct pool_allocator;

  template<typename _Tp>
    struct __allocator_always_compares_equal<pool_allocator<_Tp>>
    { static const bool value = true; };

  template<typename _Tp>
    const bool __allocator_always_compares_equal<pool_allocator<_Tp>>::value;
#endif

template<typename _Alloc>
  struct __alloc_traits
#if __cplusplus >= 201103L
  : std::allocator_traits<_Alloc>
#endif
  {
    typedef _Alloc allocator_type;
#if __cplusplus >= 201103L
    typedef std::allocator_traits<_Alloc>           _Base_type;
    typedef typename _Base_type::value_type         value_type;
    typedef typename _Base_type::pointer            pointer;
    typedef typename _Base_type::const_pointer      const_pointer;
    typedef typename _Base_type::size_type          size_type;
    typedef typename _Base_type::difference_type    difference_type;
    // C++0x allocators do not define reference or const_reference
    typedef value_type&                             reference;
    typedef const value_type&                       const_reference;
    using _Base_type::allocate;
    using _Base_type::deallocate;
    using _Base_type::construct;
    using _Base_type::destroy;
    using _Base_type::max_size;

  private:
    template<typename _Ptr>
      struct __is_custom_pointer
      : std::integral_constant<bool, std::is_same<pointer, _Ptr>::value
                                     && !std::is_pointer<_Ptr>::value>
      { };

  public:
    // overload construct for non-standard pointer types
    template<typename _Ptr, typename... _Args>
      static typename std::enable_if<__is_custom_pointer<_Ptr>::value>::type
      construct(_Alloc& __a, _Ptr __p, _Args&&... __args)
      {
    _Base_type::construct(__a, std::addressof(*__p),
                  std::forward<_Args>(__args)...);
      }

    // overload destroy for non-standard pointer types
    template<typename _Ptr>
      static typename std::enable_if<__is_custom_pointer<_Ptr>::value>::type
      destroy(_Alloc& __a, _Ptr __p)
      { _Base_type::destroy(__a, std::addressof(*__p)); }

    static _Alloc _S_select_on_copy(const _Alloc& __a)
    { return _Base_type::select_on_container_copy_construction(__a); }

    static void _S_on_swap(_Alloc& __a, _Alloc& __b)
    { std::__alloc_on_swap(__a, __b); }

    static constexpr bool _S_propagate_on_copy_assign()
    { return _Base_type::propagate_on_container_copy_assignment::value; }

    static constexpr bool _S_propagate_on_move_assign()
    { return _Base_type::propagate_on_container_move_assignment::value; }

    static constexpr bool _S_propagate_on_swap()
    { return _Base_type::propagate_on_container_swap::value; }

    static constexpr bool _S_always_equal()
    { return __allocator_always_compares_equal<_Alloc>::value; }

    static constexpr bool _S_nothrow_move()
    { return _S_propagate_on_move_assign() || _S_always_equal(); }

    static constexpr bool _S_nothrow_swap()
    {
      using std::swap;
      return !_S_propagate_on_swap()
        || noexcept(swap(std::declval<_Alloc&>(), std::declval<_Alloc&>()));
    }

    template<typename _Tp>
      struct rebind
      { typedef typename _Base_type::template rebind_alloc<_Tp> other; };
#else

    typedef typename _Alloc::pointer                pointer;
    typedef typename _Alloc::const_pointer          const_pointer;
    typedef typename _Alloc::value_type             value_type;
    typedef typename _Alloc::reference              reference;
    typedef typename _Alloc::const_reference        const_reference;
    typedef typename _Alloc::size_type              size_type;
    typedef typename _Alloc::difference_type        difference_type;

    static pointer
    allocate(_Alloc& __a, size_type __n)
    { return __a.allocate(__n); }

    static void deallocate(_Alloc& __a, pointer __p, size_type __n)
    { __a.deallocate(__p, __n); }

    template<typename _Tp>
      static void construct(_Alloc& __a, pointer __p, const _Tp& __arg)
      { __a.construct(__p, __arg); }

    static void destroy(_Alloc& __a, pointer __p)
    { __a.destroy(__p); }

    static size_type max_size(const _Alloc& __a)
    { return __a.max_size(); }

    static const _Alloc& _S_select_on_copy(const _Alloc& __a) { return __a; }

    static void _S_on_swap(_Alloc& __a, _Alloc& __b)
    {
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 431. Swapping containers with unequal allocators.
      std::__alloc_swap<_Alloc>::_S_do_it(__a, __b);
    }

    template<typename _Tp>
      struct rebind
      { typedef typename _Alloc::template rebind<_Tp>::other other; };
#endif
  };

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std