diff mbox

Limit template parameters in hashtable

Message ID 5200B682.7010706@gmail.com
State New
Headers show

Commit Message

François Dumont Aug. 6, 2013, 8:40 a.m. UTC 
Ok then attached patch applied.

2013-08-06  François Dumont  <fdumont@gcc.gnu.org>

     * include/bits/hashtable_policy.h (_Hashtable_alloc): New.
     (_ReuseOrAllocNode, _AllocNode): Adapt to use latter rather than
     _Hashtable.
     (_Before_begin<>): Remove.
     * include/bits/hashtable.h (_Hashtable): Inherit from
     _Hashtable_alloc and adapt. Restore _M_before_begin field.
     * python/libstdcxx/v6/printers.py (StdHashtableIterator): Adapt
     access to hashtable before begin.
     * testsuite/23_containers/unordered_set/
     not_default_constructible_hash_neg.cc: Adapt dg-error line number.
     * testsuite/23_containers/unordered_set/instantiation_neg.cc:
     Likewise.

François


On 08/05/2013 11:39 AM, Jonathan Wakely wrote:
> On 28 July 2013 17:44, François Dumont wrote:
>> Is it ok for this one ?
> Yes, sorry for the delay, this is OK to commit.  I think the code is
> cleaner now, and I agree with your EBO improvement that puts _M_before
> _begin back in the main hashtable.
>
> Thanks very much for doing this.
>
diff mbox

Patch

Index: include/bits/hashtable_policy.h
===================================================================
--- include/bits/hashtable_policy.h	(revision 201521)
+++ include/bits/hashtable_policy.h	(working copy)
@@ -102,25 +102,26 @@ 
       { return std::get<0>(std::forward<_Tp>(__x)); }
   };
 
+  template<typename _NodeAlloc>
+    struct _Hashtable_alloc;
+
   // Functor recycling a pool of nodes and using allocation once the pool is
   // empty.
-  template<typename _Key, typename _Value, typename _Alloc,
-	   typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash,
-	   typename _RehashPolicy, typename _Traits>
+  template<typename _NodeAlloc>
     struct _ReuseOrAllocNode
     {
     private:
-      using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
-				     _Equal, _H1, _H2, _Hash,
-				     _RehashPolicy, _Traits>;
-      using __val_alloc_type = typename __hashtable::_Value_alloc_type;
-      using __val_alloc_traits = typename __hashtable::_Value_alloc_traits;
-      using __node_alloc_traits = typename __hashtable::_Node_alloc_traits;
-      using __node_type = typename __hashtable::__node_type;
+      using __node_alloc_type = _NodeAlloc;
+      using __hashtable_alloc = _Hashtable_alloc<__node_alloc_type>;
+      using __value_alloc_type = typename __hashtable_alloc::__value_alloc_type;
+      using __value_alloc_traits =
+	typename __hashtable_alloc::__value_alloc_traits;
+      using __node_alloc_traits =
+	typename __hashtable_alloc::__node_alloc_traits;
+      using __node_type = typename __hashtable_alloc::__node_type;
 
     public:
-      _ReuseOrAllocNode(__node_type* __nodes, __hashtable& __h)
+      _ReuseOrAllocNode(__node_type* __nodes, __hashtable_alloc& __h)
 	: _M_nodes(__nodes), _M_h(__h) { }
       _ReuseOrAllocNode(const _ReuseOrAllocNode&) = delete;
 
@@ -136,12 +137,12 @@ 
 	      __node_type* __node = _M_nodes;
 	      _M_nodes = _M_nodes->_M_next();
 	      __node->_M_nxt = nullptr;
-	      __val_alloc_type __a(_M_h._M_node_allocator());
-	      __val_alloc_traits::destroy(__a, __node->_M_valptr());
+	      __value_alloc_type __a(_M_h._M_node_allocator());
+	      __value_alloc_traits::destroy(__a, __node->_M_valptr());
 	      __try
 		{
-		  __val_alloc_traits::construct(__a, __node->_M_valptr(),
-						std::forward<_Arg>(__arg));
+		  __value_alloc_traits::construct(__a, __node->_M_valptr(),
+						  std::forward<_Arg>(__arg));
 		}
 	      __catch(...)
 		{
@@ -157,24 +158,19 @@ 
 
     private:
       mutable __node_type* _M_nodes;
-      __hashtable& _M_h;
+      __hashtable_alloc& _M_h;
     };
 
   // Functor similar to the previous one but without any pool of node to recycle.
-  template<typename _Key, typename _Value, typename _Alloc,
-	   typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash,
-	   typename _RehashPolicy, typename _Traits>
+  template<typename _NodeAlloc>
     struct _AllocNode
     {
     private:
-      using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
-				     _Equal, _H1, _H2, _Hash,
-				     _RehashPolicy, _Traits>;
-      using __node_type = typename __hashtable::__node_type;
+      using __hashtable_alloc = _Hashtable_alloc<_NodeAlloc>;
+      using __node_type = typename __hashtable_alloc::__node_type;
 
     public:
-      _AllocNode(__hashtable& __h)
+      _AllocNode(__hashtable_alloc& __h)
 	: _M_h(__h) { }
 
       template<typename _Arg>
@@ -183,7 +179,7 @@ 
 	{ return _M_h._M_allocate_node(std::forward<_Arg>(__arg)); }
 
     private:
-      __hashtable& _M_h;
+      __hashtable_alloc& _M_h;
     };
 
   // Auxiliary types used for all instantiations of _Hashtable nodes
@@ -247,6 +243,8 @@ 
   template<typename _Value>
     struct _Hash_node_value_base : _Hash_node_base
     {
+      typedef _Value value_type;
+
       __gnu_cxx::__aligned_buffer<_Value> _M_storage;
 
       _Value*
@@ -336,9 +334,9 @@ 
       using __node_type = typename __base_type::__node_type;
 
     public:
-      typedef _Value                                   value_type;
-      typedef std::ptrdiff_t                           difference_type;
-      typedef std::forward_iterator_tag                iterator_category;
+      typedef _Value					value_type;
+      typedef std::ptrdiff_t				difference_type;
+      typedef std::forward_iterator_tag			iterator_category;
 
       using pointer = typename std::conditional<__constant_iterators,
 						const _Value*, _Value*>::type;
@@ -387,12 +385,12 @@ 
       using __node_type = typename __base_type::__node_type;
 
     public:
-      typedef _Value                                   value_type;
-      typedef std::ptrdiff_t                           difference_type;
-      typedef std::forward_iterator_tag                iterator_category;
+      typedef _Value					value_type;
+      typedef std::ptrdiff_t				difference_type;
+      typedef std::forward_iterator_tag			iterator_category;
 
-      typedef const _Value*                            pointer;
-      typedef const _Value&                            reference;
+      typedef const _Value*				pointer;
+      typedef const _Value&				reference;
 
       _Node_const_iterator()
       : __base_type(0) { }
@@ -499,8 +497,8 @@ 
 
     static const std::size_t _S_growth_factor = 2;
 
-    float                _M_max_load_factor;
-    mutable std::size_t  _M_next_resize;
+    float		_M_max_load_factor;
+    mutable std::size_t	_M_next_resize;
   };
 
   // Base classes for std::_Hashtable.  We define these base classes
@@ -697,9 +695,10 @@ 
 
       using __unique_keys = typename __hashtable_base::__unique_keys;
       using __ireturn_type = typename __hashtable_base::__ireturn_type;
-      using __node_gen_type = _AllocNode<_Key, _Value, _Alloc, _ExtractKey,
-					 _Equal, _H1, _H2, _Hash,
-					 _RehashPolicy, _Traits>;
+      using __node_type = _Hash_node<_Value, _Traits::__hash_cached::value>;
+      using __node_alloc_type =
+	typename __alloctr_rebind<_Alloc, __node_type>::__type;
+      using __node_gen_type = _AllocNode<__node_alloc_type>;
 
       __hashtable&
       _M_conjure_hashtable()
@@ -979,8 +978,10 @@ 
     {
       _Hashtable_ebo_helper() = default;
 
-      _Hashtable_ebo_helper(const _Tp& __tp) : _Tp(__tp)
-      { }
+      template<typename _OtherTp>
+	_Hashtable_ebo_helper(_OtherTp&& __tp)
+	  : _Tp(std::forward<_OtherTp>(__tp))
+	{ }
 
       static const _Tp&
       _S_cget(const _Hashtable_ebo_helper& __eboh)
@@ -997,8 +998,10 @@ 
     {
       _Hashtable_ebo_helper() = default;
 
-      _Hashtable_ebo_helper(const _Tp& __tp) : _M_tp(__tp)
-      { }
+      template<typename _OtherTp>
+	_Hashtable_ebo_helper(_OtherTp&& __tp)
+	  : _M_tp(std::forward<_OtherTp>(__tp))
+	{ }
 
       static const _Tp&
       _S_cget(const _Hashtable_ebo_helper& __eboh)
@@ -1431,15 +1434,15 @@ 
 					       _H1, _H2, _Hash, __cache>;
       using __hash_code_base = typename __base_type::__hash_code_base;
     public:
-      typedef _Value                                   value_type;
+      typedef _Value					value_type;
       typedef typename std::conditional<__constant_iterators,
 					const _Value*, _Value*>::type
 						       pointer;
       typedef typename std::conditional<__constant_iterators,
 					const _Value&, _Value&>::type
 						       reference;
-      typedef std::ptrdiff_t                           difference_type;
-      typedef std::forward_iterator_tag                iterator_category;
+      typedef std::ptrdiff_t				difference_type;
+      typedef std::forward_iterator_tag			iterator_category;
 
       _Local_iterator() = default;
 
@@ -1487,11 +1490,11 @@ 
       using __hash_code_base = typename __base_type::__hash_code_base;
 
     public:
-      typedef _Value                                   value_type;
-      typedef const _Value*                            pointer;
-      typedef const _Value&                            reference;
-      typedef std::ptrdiff_t                           difference_type;
-      typedef std::forward_iterator_tag                iterator_category;
+      typedef _Value					value_type;
+      typedef const _Value*				pointer;
+      typedef const _Value&				reference;
+      typedef std::ptrdiff_t				difference_type;
+      typedef std::forward_iterator_tag			iterator_category;
 
       _Local_const_iterator() = default;
 
@@ -1551,11 +1554,11 @@ 
     private _Hashtable_ebo_helper<0, _Equal>
   {
   public:
-    typedef _Key                                    key_type;
-    typedef _Value                                  value_type;
-    typedef _Equal                                  key_equal;
-    typedef std::size_t                             size_type;
-    typedef std::ptrdiff_t                          difference_type;
+    typedef _Key					key_type;
+    typedef _Value					value_type;
+    typedef _Equal					key_equal;
+    typedef std::size_t					size_type;
+    typedef std::ptrdiff_t				difference_type;
 
     using __traits_type = _Traits;
     using __hash_cached = typename __traits_type::__hash_cached;
@@ -1597,9 +1600,6 @@ 
 					__hash_code, __hash_cached::value>;
 
   protected:
-    using __node_base = __detail::_Hash_node_base;
-    using __bucket_type = __node_base*;
-
     _Hashtable_base(const _ExtractKey& __ex, const _H1& __h1, const _H2& __h2,
 		    const _Hash& __hash, const _Equal& __eq)
     : __hash_code_base(__ex, __h1, __h2, __hash), _EqualEBO(__eq)
@@ -1787,23 +1787,136 @@ 
     }
 
   /**
-   * This type is to combine a _Hash_node_base instance with an allocator
-   * instance through inheritance to benefit from EBO when possible.
+   * This type deals with all allocation and keeps an allocator instance through
+   * inheritance to benefit from EBO when possible.
    */
   template<typename _NodeAlloc>
-    struct _Before_begin : public _NodeAlloc
+    struct _Hashtable_alloc : private _Hashtable_ebo_helper<0, _NodeAlloc>
     {
-      _Hash_node_base _M_node;
+    private:
+      using __ebo_node_alloc = _Hashtable_ebo_helper<0, _NodeAlloc>;
+    public:
+      using __node_type = typename _NodeAlloc::value_type;
+      using __node_alloc_type = _NodeAlloc;
+      // Use __gnu_cxx to benefit from _S_always_equal and al.
+      using __node_alloc_traits = __gnu_cxx::__alloc_traits<__node_alloc_type>;
 
-      _Before_begin(const _Before_begin&) = default;
-      _Before_begin(_Before_begin&&) = default;
+      using __value_type = typename __node_type::value_type;
+      using __value_alloc_type =
+	typename __alloctr_rebind<__node_alloc_type, __value_type>::__type;
+      using __value_alloc_traits = std::allocator_traits<__value_alloc_type>;
 
+      using __node_base = __detail::_Hash_node_base;
+      using __bucket_type = __node_base*;      
+      using __bucket_alloc_type =
+	typename __alloctr_rebind<__node_alloc_type, __bucket_type>::__type;
+      using __bucket_alloc_traits = std::allocator_traits<__bucket_alloc_type>;
+
+      _Hashtable_alloc(const _Hashtable_alloc&) = default;
+      _Hashtable_alloc(_Hashtable_alloc&&) = default;
+
       template<typename _Alloc>
-	_Before_begin(_Alloc&& __a)
-	  : _NodeAlloc(std::forward<_Alloc>(__a))
+	_Hashtable_alloc(_Alloc&& __a)
+	  : __ebo_node_alloc(std::forward<_Alloc>(__a))
 	{ }
+
+      __node_alloc_type&
+      _M_node_allocator()
+      { return __ebo_node_alloc::_S_get(*this); }
+
+      const __node_alloc_type&
+      _M_node_allocator() const
+      { return __ebo_node_alloc::_S_cget(*this); }
+
+      template<typename... _Args>
+	__node_type*
+	_M_allocate_node(_Args&&... __args);
+
+      void
+      _M_deallocate_node(__node_type* __n);
+
+      // Deallocate the linked list of nodes pointed to by __n
+      void
+      _M_deallocate_nodes(__node_type* __n);
+
+      __bucket_type*
+      _M_allocate_buckets(std::size_t __n);
+
+      void
+      _M_deallocate_buckets(__bucket_type*, std::size_t __n);
     };
 
+  // Definitions of class template _Hashtable_alloc's out-of-line member
+  // functions.
+  template<typename _NodeAlloc>
+    template<typename... _Args>
+      typename _Hashtable_alloc<_NodeAlloc>::__node_type*
+      _Hashtable_alloc<_NodeAlloc>::_M_allocate_node(_Args&&... __args)
+      {
+	auto __nptr = __node_alloc_traits::allocate(_M_node_allocator(), 1);
+	__node_type* __n = std::__addressof(*__nptr);
+	__try
+	  {
+	    __value_alloc_type __a(_M_node_allocator());
+	    ::new ((void*)__n) __node_type();
+	    __value_alloc_traits::construct(__a, __n->_M_valptr(),
+					    std::forward<_Args>(__args)...);
+	    return __n;
+	  }
+	__catch(...)
+	  {
+	    __node_alloc_traits::deallocate(_M_node_allocator(), __nptr, 1);
+	    __throw_exception_again;
+	  }
+      }
+
+  template<typename _NodeAlloc>
+    void
+    _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node(__node_type* __n)
+    {
+      typedef typename __node_alloc_traits::pointer _Ptr;
+      auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__n);
+      __value_alloc_type __a(_M_node_allocator());
+      __value_alloc_traits::destroy(__a, __n->_M_valptr());
+      __n->~__node_type();
+      __node_alloc_traits::deallocate(_M_node_allocator(), __ptr, 1);
+    }
+
+  template<typename _NodeAlloc>
+    void
+    _Hashtable_alloc<_NodeAlloc>::_M_deallocate_nodes(__node_type* __n)
+    {
+      while (__n)
+	{
+	  __node_type* __tmp = __n;
+	  __n = __n->_M_next();
+	  _M_deallocate_node(__tmp);
+	}
+    }
+
+  template<typename _NodeAlloc>
+    typename _Hashtable_alloc<_NodeAlloc>::__bucket_type*
+    _Hashtable_alloc<_NodeAlloc>::_M_allocate_buckets(std::size_t __n)
+    {
+      __bucket_alloc_type __alloc(_M_node_allocator());
+
+      auto __ptr = __bucket_alloc_traits::allocate(__alloc, __n);
+      __bucket_type* __p = std::__addressof(*__ptr);
+      __builtin_memset(__p, 0, __n * sizeof(__bucket_type));
+      return __p;
+    }
+
+  template<typename _NodeAlloc>
+    void
+    _Hashtable_alloc<_NodeAlloc>::_M_deallocate_buckets(__bucket_type* __bkts,
+							std::size_t __n)
+    {
+      typedef typename __bucket_alloc_traits::pointer _Ptr;
+      auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__bkts);
+      __bucket_alloc_type __alloc(_M_node_allocator());
+      __bucket_alloc_traits::deallocate(__alloc, __ptr, __n);
+    }
+
  //@} hashtable-detail
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace __detail
Index: include/bits/hashtable.h
===================================================================
--- include/bits/hashtable.h	(revision 201521)
+++ include/bits/hashtable.h	(working copy)
@@ -103,7 +103,7 @@ 
    *  Each _Hashtable data structure has:
    *
    *  - _Bucket[]       _M_buckets
-   *  - _Hash_node_base _M_bbegin
+   *  - _Hash_node_base _M_before_begin
    *  - size_type       _M_bucket_count
    *  - size_type       _M_element_count
    *
@@ -181,13 +181,27 @@ 
       public __detail::_Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 				    _H1, _H2, _Hash, _RehashPolicy, _Traits>,
       public __detail::_Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-				 _H1, _H2, _Hash, _RehashPolicy, _Traits>
+				 _H1, _H2, _Hash, _RehashPolicy, _Traits>,
+      private __detail::_Hashtable_alloc<
+	typename __alloctr_rebind<_Alloc,
+	  __detail::_Hash_node<_Value,
+			       _Traits::__hash_cached::value> >::__type>
     {
-      typedef std::allocator_traits<_Alloc> _Alloc_traits;
-      typedef typename _Alloc_traits::template rebind_alloc<_Value>
-							_Value_alloc_type;
-      typedef __gnu_cxx::__alloc_traits<_Value_alloc_type> _Value_alloc_traits;
+      using __traits_type = _Traits;
+      using __hash_cached = typename __traits_type::__hash_cached;
+      using __node_type = __detail::_Hash_node<_Value, __hash_cached::value>;
+      using __node_alloc_type =
+	typename __alloctr_rebind<_Alloc, __node_type>::__type;
 
+      using __hashtable_alloc = __detail::_Hashtable_alloc<__node_alloc_type>;
+
+      using __value_alloc_traits =
+	typename __hashtable_alloc::__value_alloc_traits;
+      using __node_alloc_traits =
+	typename __hashtable_alloc::__node_alloc_traits;
+      using __node_base = typename __hashtable_alloc::__node_base;
+      using __bucket_type = typename __hashtable_alloc::__bucket_type;
+
     public:
       typedef _Key						key_type;
       typedef _Value						value_type;
@@ -196,8 +210,8 @@ 
 
       // mapped_type, if present, comes from _Map_base.
       // hasher, if present, comes from _Hash_code_base/_Hashtable_base.
-      typedef typename _Value_alloc_traits::pointer		pointer;
-      typedef typename _Value_alloc_traits::const_pointer	const_pointer;
+      typedef typename __value_alloc_traits::pointer		pointer;
+      typedef typename __value_alloc_traits::const_pointer	const_pointer;
       typedef value_type&					reference;
       typedef const value_type&					const_reference;
 
@@ -205,8 +219,6 @@ 
       using __rehash_type = _RehashPolicy;
       using __rehash_state = typename __rehash_type::_State;
 
-      using __traits_type = _Traits;
-      using __hash_cached = typename __traits_type::__hash_cached;
       using __constant_iterators = typename __traits_type::__constant_iterators;
       using __unique_keys = typename __traits_type::__unique_keys;
 
@@ -221,9 +233,6 @@ 
 
       using __hash_code_base =  typename __hashtable_base::__hash_code_base;
       using __hash_code =  typename __hashtable_base::__hash_code;
-      using __node_type = typename __hashtable_base::__node_type;
-      using __node_base = typename __hashtable_base::__node_base;
-      using __bucket_type = typename __hashtable_base::__bucket_type;
       using __ireturn_type = typename __hashtable_base::__ireturn_type;
 
       using __map_base = __detail::_Map_base<_Key, _Value, _Alloc, _ExtractKey,
@@ -240,9 +249,7 @@ 
 					    _RehashPolicy, _Traits>;
 
       using __reuse_or_alloc_node_type =
-	__detail::_ReuseOrAllocNode<_Key, _Value, _Alloc,
-				    _ExtractKey, _Equal, _H1, _H2, _Hash,
-				    _RehashPolicy, _Traits>;
+	__detail::_ReuseOrAllocNode<__node_alloc_type>;
 
       // Metaprogramming for picking apart hash caching.
       template<typename _Cond>
@@ -309,18 +316,6 @@ 
 	       bool _Constant_iteratorsa, bool _Unique_keysa>
 	friend struct __detail::_Insert;
 
-      template<typename _Keya, typename _Valuea, typename _Alloca,
-	       typename _ExtractKeya, typename _Equala,
-	       typename _H1a, typename _H2a, typename _Hasha,
-	       typename _RehashPolicya, typename _Traitsa>
-	friend struct __detail::_ReuseOrAllocNode;
-
-      template<typename _Keya, typename _Valuea, typename _Alloca,
-	       typename _ExtractKeya, typename _Equala,
-	       typename _H1a, typename _H2a, typename _Hasha,
-	       typename _RehashPolicya, typename _Traitsa>
-	friend struct __detail::_AllocNode;
-
     public:
       using size_type = typename __hashtable_base::size_type;
       using difference_type = typename __hashtable_base::difference_type;
@@ -333,60 +328,20 @@ 
 				   const_local_iterator;
 
     private:
-      typedef typename _Alloc_traits::template rebind_alloc<__node_type>
-							_Node_alloc_type;
-      // Use __gnu_cxx to benefit from _S_always_equal and al.
-      typedef __gnu_cxx::__alloc_traits<_Node_alloc_type> _Node_alloc_traits;
-
-      typedef
-      typename _Alloc_traits::template rebind_alloc<__bucket_type>
-							_Bucket_alloc_type;
-      typedef std::allocator_traits<_Bucket_alloc_type> _Bucket_alloc_traits;
-
-      using __before_begin = __detail::_Before_begin<_Node_alloc_type>;
-
       __bucket_type*		_M_buckets;
       size_type			_M_bucket_count;
-      __before_begin		_M_bbegin;
+      __node_base		_M_before_begin;
       size_type			_M_element_count;
       _RehashPolicy		_M_rehash_policy;
 
-      _Node_alloc_type&
-      _M_node_allocator()
-      { return _M_bbegin; }
+      __hashtable_alloc&
+      _M_base_alloc() { return *this; }
 
-      const _Node_alloc_type&
-      _M_node_allocator() const
-      { return _M_bbegin; }
+      using __hashtable_alloc::_M_deallocate_buckets;
 
-      __node_base&
-      _M_before_begin()
-      { return _M_bbegin._M_node; }
-
-      const __node_base&
-      _M_before_begin() const
-      { return _M_bbegin._M_node; }
-
-      template<typename... _Args>
-	__node_type*
-	_M_allocate_node(_Args&&... __args);
-
       void
-      _M_deallocate_node(__node_type* __n);
-
-      // Deallocate the linked list of nodes pointed to by __n
-      void
-      _M_deallocate_nodes(__node_type* __n);
-
-      __bucket_type*
-      _M_allocate_buckets(size_type __n);
-
-      void
-      _M_deallocate_buckets(__bucket_type*, size_type __n);
-
-      void
       _M_deallocate_buckets()
-      { _M_deallocate_buckets(_M_buckets, _M_bucket_count); }
+      { this->_M_deallocate_buckets(_M_buckets, _M_bucket_count); }
 
       // Gets bucket begin, deals with the fact that non-empty buckets contain
       // their before begin node.
@@ -395,7 +350,7 @@ 
 
       __node_type*
       _M_begin() const
-      { return static_cast<__node_type*>(_M_before_begin()._M_nxt); }
+      { return static_cast<__node_type*>(_M_before_begin._M_nxt); }
 
       template<typename _NodeGenerator>
 	void
@@ -477,11 +432,11 @@ 
 
       _Hashtable&
       operator=(_Hashtable&& __ht)
-      noexcept(_Node_alloc_traits::_S_nothrow_move())
+      noexcept(__node_alloc_traits::_S_nothrow_move())
       {
         constexpr bool __move_storage =
-          _Node_alloc_traits::_S_propagate_on_move_assign()
-          || _Node_alloc_traits::_S_always_equal();
+          __node_alloc_traits::_S_propagate_on_move_assign()
+          || __node_alloc_traits::_S_always_equal();
         _M_move_assign(std::move(__ht),
                        integral_constant<bool, __move_storage>());
 	return *this;
@@ -491,7 +446,7 @@ 
       operator=(initializer_list<value_type> __l)
       {
 	__reuse_or_alloc_node_type __roan(_M_begin(), *this);
-	_M_before_begin()._M_nxt = nullptr;
+	_M_before_begin._M_nxt = nullptr;
 	clear();
 	this->_M_insert_range(__l.begin(), __l.end(), __roan);
 	return *this;
@@ -501,7 +456,7 @@ 
 
       void
       swap(_Hashtable&)
-      noexcept(_Node_alloc_traits::_S_nothrow_swap());
+      noexcept(__node_alloc_traits::_S_nothrow_swap());
 
       // Basic container operations
       iterator
@@ -538,11 +493,11 @@ 
 
       allocator_type
       get_allocator() const noexcept
-      { return allocator_type(_M_node_allocator()); }
+      { return allocator_type(this->_M_node_allocator()); }
 
       size_type
       max_size() const noexcept
-      { return _Node_alloc_traits::max_size(_M_node_allocator()); }
+      { return __node_alloc_traits::max_size(this->_M_node_allocator()); }
 
       // Observers
       key_equal
@@ -807,101 +762,6 @@ 
 	   typename _Alloc, typename _ExtractKey, typename _Equal,
 	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
 	   typename _Traits>
-    template<typename... _Args>
-      typename _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-			  _H1, _H2, _Hash, _RehashPolicy, _Traits>::__node_type*
-      _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-		 _H1, _H2, _Hash, _RehashPolicy, _Traits>::
-      _M_allocate_node(_Args&&... __args)
-      {
-	auto __nptr = _Node_alloc_traits::allocate(_M_node_allocator(), 1);
-	__node_type* __n = std::__addressof(*__nptr);
-	__try
-	  {
-	    _Value_alloc_type __a(_M_node_allocator());
-	    ::new ((void*)__n) __node_type();
-	    _Value_alloc_traits::construct(__a, __n->_M_valptr(),
-					   std::forward<_Args>(__args)...);
-	    return __n;
-	  }
-	__catch(...)
-	  {
-	    _Node_alloc_traits::deallocate(_M_node_allocator(), __nptr, 1);
-	    __throw_exception_again;
-	  }
-      }
-
-  template<typename _Key, typename _Value,
-	   typename _Alloc, typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
-	   typename _Traits>
-    void
-    _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
-    _M_deallocate_node(__node_type* __n)
-    {
-      typedef typename _Node_alloc_traits::pointer _Ptr;
-      auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__n);
-      _Value_alloc_type __a(_M_node_allocator());
-      _Value_alloc_traits::destroy(__a, __n->_M_valptr());
-      __n->~__node_type();
-      _Node_alloc_traits::deallocate(_M_node_allocator(), __ptr, 1);
-    }
-
-  template<typename _Key, typename _Value,
-	   typename _Alloc, typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
-	   typename _Traits>
-    void
-    _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
-    _M_deallocate_nodes(__node_type* __n)
-    {
-      while (__n)
-	{
-	  __node_type* __tmp = __n;
-	  __n = __n->_M_next();
-	  _M_deallocate_node(__tmp);
-	}
-    }
-
-  template<typename _Key, typename _Value,
-	   typename _Alloc, typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
-	   typename _Traits>
-    typename _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-			_H1, _H2, _Hash, _RehashPolicy, _Traits>::__bucket_type*
-    _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
-    _M_allocate_buckets(size_type __n)
-    {
-      _Bucket_alloc_type __alloc(_M_node_allocator());
-
-      auto __ptr = _Bucket_alloc_traits::allocate(__alloc, __n);
-      __bucket_type* __p = std::__addressof(*__ptr);
-      __builtin_memset(__p, 0, __n * sizeof(__bucket_type));
-      return __p;
-    }
-
-  template<typename _Key, typename _Value,
-	   typename _Alloc, typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
-	   typename _Traits>
-    void
-    _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
-    _M_deallocate_buckets(__bucket_type* __bkts, size_type __n)
-    {
-      typedef typename _Bucket_alloc_traits::pointer _Ptr;
-      auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__bkts);
-      _Bucket_alloc_type __alloc(_M_node_allocator());
-      _Bucket_alloc_traits::deallocate(__alloc, __ptr, __n);
-    }
-
-  template<typename _Key, typename _Value,
-	   typename _Alloc, typename _ExtractKey, typename _Equal,
-	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
-	   typename _Traits>
     typename _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 			_Equal, _H1, _H2, _Hash, _RehashPolicy,
 			_Traits>::__node_type*
@@ -926,12 +786,12 @@ 
     : __hashtable_base(__exk, __h1, __h2, __h, __eq),
       __map_base(),
       __rehash_base(),
-      _M_bbegin(__a),
+      __hashtable_alloc(__node_alloc_type(__a)),
       _M_element_count(0),
       _M_rehash_policy()
     {
       _M_bucket_count = _M_rehash_policy._M_next_bkt(__bucket_hint);
-      _M_buckets = _M_allocate_buckets(_M_bucket_count);
+      _M_buckets = this->_M_allocate_buckets(_M_bucket_count);
     }
 
   template<typename _Key, typename _Value,
@@ -949,7 +809,7 @@ 
       : __hashtable_base(__exk, __h1, __h2, __h, __eq),
 	__map_base(),
 	__rehash_base(),
-	_M_bbegin(__a),
+	__hashtable_alloc(__node_alloc_type(__a)),
 	_M_element_count(0),
 	_M_rehash_policy()
       {
@@ -959,7 +819,7 @@ 
 	    std::max(_M_rehash_policy._M_bkt_for_elements(__nb_elems),
 		     __bucket_hint));
 
-	_M_buckets = _M_allocate_buckets(_M_bucket_count);
+	_M_buckets = this->_M_allocate_buckets(_M_bucket_count);
 	__try
 	  {
 	    for (; __f != __l; ++__f)
@@ -987,15 +847,15 @@ 
 	if (&__ht == this)
 	  return *this;
 
-	if (_Node_alloc_traits::_S_propagate_on_copy_assign())
+	if (__node_alloc_traits::_S_propagate_on_copy_assign())
 	  {
 	    auto& __this_alloc = this->_M_node_allocator();
 	    auto& __that_alloc = __ht._M_node_allocator();
-	    if (!_Node_alloc_traits::_S_always_equal()
+	    if (!__node_alloc_traits::_S_always_equal()
 		&& __this_alloc != __that_alloc)
 	      {
 		// Replacement allocator cannot free existing storage.
-		_M_deallocate_nodes(_M_begin());
+		this->_M_deallocate_nodes(_M_begin());
 		if (__builtin_expect(_M_bucket_count != 0, true))
 		  _M_deallocate_buckets();
 		_M_reset();
@@ -1008,7 +868,7 @@ 
 		  {
 		    _M_assign(__ht,
 			      [this](const __node_type* __n)
-			      { return _M_allocate_node(__n->_M_v()); });
+			      { return this->_M_allocate_node(__n->_M_v()); });
 		  }
 		__catch(...)
 		  {
@@ -1030,7 +890,7 @@ 
 	if (_M_bucket_count != __ht._M_bucket_count)
 	  {
 	    __former_buckets = _M_buckets;
-	    _M_buckets = _M_allocate_buckets(__ht._M_bucket_count);
+	    _M_buckets = this->_M_allocate_buckets(__ht._M_bucket_count);
 	    _M_bucket_count = __ht._M_bucket_count;
 	  }
 	else
@@ -1043,12 +903,13 @@ 
 	    _M_element_count = __ht._M_element_count;
 	    _M_rehash_policy = __ht._M_rehash_policy;
 	    __reuse_or_alloc_node_type __roan(_M_begin(), *this);
-	    _M_before_begin()._M_nxt = nullptr;
+	    _M_before_begin._M_nxt = nullptr;
 	    _M_assign(__ht, 
 		      [&__roan](const __node_type* __n)
 		      { return __roan(__n->_M_v()); });
 	    if (__former_buckets)
-	      _M_deallocate_buckets(__former_buckets, __former_bucket_count);
+	      this->_M_deallocate_buckets(__former_buckets,
+					  __former_bucket_count);
 	  }
 	__catch(...)
 	  {
@@ -1079,11 +940,11 @@ 
       {
 	__bucket_type* __buckets = nullptr;
 	if (!_M_buckets)
-	  _M_buckets = __buckets = _M_allocate_buckets(_M_bucket_count);
+	  _M_buckets = __buckets = this->_M_allocate_buckets(_M_bucket_count);
 
 	__try
 	  {
-	    if (!__ht._M_before_begin()._M_nxt)
+	    if (!__ht._M_before_begin._M_nxt)
 	      return;
 
 	    // First deal with the special first node pointed to by
@@ -1091,8 +952,8 @@ 
 	    __node_type* __ht_n = __ht._M_begin();
 	    __node_type* __this_n = __node_gen(__ht_n);
 	    this->_M_copy_code(__this_n, __ht_n);
-	    _M_before_begin()._M_nxt = __this_n;
-	    _M_buckets[_M_bucket_index(__this_n)] = &_M_before_begin();
+	    _M_before_begin._M_nxt = __this_n;
+	    _M_buckets[_M_bucket_index(__this_n)] = &_M_before_begin;
 
 	    // Then deal with other nodes.
 	    __node_base* __prev_n = __this_n;
@@ -1128,7 +989,7 @@ 
       _M_rehash_policy._M_reset();
       _M_bucket_count = 0;
       _M_buckets = nullptr;
-      _M_before_begin()._M_nxt = nullptr;
+      _M_before_begin._M_nxt = nullptr;
       _M_element_count = 0;
     }
 
@@ -1141,7 +1002,7 @@ 
 	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
     _M_move_assign(_Hashtable&& __ht, std::true_type)
     {
-      _M_deallocate_nodes(_M_begin());
+      this->_M_deallocate_nodes(_M_begin());
       if (__builtin_expect(_M_bucket_count != 0, true))
 	_M_deallocate_buckets();
 
@@ -1149,14 +1010,14 @@ 
       _M_rehash_policy = __ht._M_rehash_policy;
       _M_buckets = __ht._M_buckets;
       _M_bucket_count = __ht._M_bucket_count;
-      _M_before_begin()._M_nxt = __ht._M_before_begin()._M_nxt;
+      _M_before_begin._M_nxt = __ht._M_before_begin._M_nxt;
       _M_element_count = __ht._M_element_count;
-      std::__alloc_on_move(_M_node_allocator(), __ht._M_node_allocator());
+      std::__alloc_on_move(this->_M_node_allocator(), __ht._M_node_allocator());
 
       // Fix buckets containing the _M_before_begin pointers that can't be
       // moved.
       if (_M_begin())
-	_M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin();
+	_M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin;
       __ht._M_reset();
     }
 
@@ -1169,7 +1030,7 @@ 
 	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
     _M_move_assign(_Hashtable&& __ht, std::false_type)
     {
-      if (__ht._M_node_allocator() == _M_node_allocator())
+      if (__ht._M_node_allocator() == this->_M_node_allocator())
 	_M_move_assign(std::move(__ht), std::true_type());
       else
 	{
@@ -1181,7 +1042,7 @@ 
 	  if (_M_bucket_count != __ht._M_bucket_count)
 	    {
 	      __former_buckets = _M_buckets;
-	      _M_buckets = _M_allocate_buckets(__ht._M_bucket_count);
+	      _M_buckets = this->_M_allocate_buckets(__ht._M_bucket_count);
 	      _M_bucket_count = __ht._M_bucket_count;
 	    }
 	  else
@@ -1194,7 +1055,7 @@ 
 	      _M_element_count = __ht._M_element_count;
 	      _M_rehash_policy = __ht._M_rehash_policy;
 	      __reuse_or_alloc_node_type __roan(_M_begin(), *this);
-	      _M_before_begin()._M_nxt = nullptr;
+	      _M_before_begin._M_nxt = nullptr;
 	      _M_assign(__ht,
 			[&__roan](__node_type* __n)
 			{ return __roan(std::move_if_noexcept(__n->_M_v())); });
@@ -1226,16 +1087,16 @@ 
     : __hashtable_base(__ht),
       __map_base(__ht),
       __rehash_base(__ht),
+      __hashtable_alloc(
+	__node_alloc_traits::_S_select_on_copy(__ht._M_node_allocator())),
       _M_buckets(),
       _M_bucket_count(__ht._M_bucket_count),
-      _M_bbegin(_Node_alloc_traits::_S_select_on_copy(
-		__ht._M_node_allocator())),
       _M_element_count(__ht._M_element_count),
       _M_rehash_policy(__ht._M_rehash_policy)
     {
       _M_assign(__ht,
 		[this](const __node_type* __n)
-		{ return _M_allocate_node(__n->_M_v()); });
+		{ return this->_M_allocate_node(__n->_M_v()); });
     }
 
   template<typename _Key, typename _Value,
@@ -1248,16 +1109,17 @@ 
     : __hashtable_base(__ht),
       __map_base(__ht),
       __rehash_base(__ht),
+      __hashtable_alloc(std::move(__ht._M_base_alloc())),
       _M_buckets(__ht._M_buckets),
       _M_bucket_count(__ht._M_bucket_count),
-      _M_bbegin(std::move(__ht._M_bbegin)),
+      _M_before_begin(__ht._M_before_begin._M_nxt),
       _M_element_count(__ht._M_element_count),
       _M_rehash_policy(__ht._M_rehash_policy)
     {
       // Update, if necessary, bucket pointing to before begin that hasn't
       // moved.
       if (_M_begin())
-	_M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin();
+	_M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin;
       __ht._M_reset();
     }
 
@@ -1271,15 +1133,15 @@ 
     : __hashtable_base(__ht),
       __map_base(__ht),
       __rehash_base(__ht),
+      __hashtable_alloc(__node_alloc_type(__a)),
       _M_buckets(),
       _M_bucket_count(__ht._M_bucket_count),
-      _M_bbegin(_Node_alloc_type(__a)),
       _M_element_count(__ht._M_element_count),
       _M_rehash_policy(__ht._M_rehash_policy)
     {
       _M_assign(__ht,
 		[this](const __node_type* __n)
-		{ return _M_allocate_node(__n->_M_v()); });
+		{ return this->_M_allocate_node(__n->_M_v()); });
     }
 
   template<typename _Key, typename _Value,
@@ -1292,20 +1154,20 @@ 
     : __hashtable_base(__ht),
       __map_base(__ht),
       __rehash_base(__ht),
+      __hashtable_alloc(__node_alloc_type(__a)),
       _M_buckets(),
       _M_bucket_count(__ht._M_bucket_count),
-      _M_bbegin(_Node_alloc_type(__a)),
       _M_element_count(__ht._M_element_count),
       _M_rehash_policy(__ht._M_rehash_policy)
     {
-      if (__ht._M_node_allocator() == _M_node_allocator())
+      if (__ht._M_node_allocator() == this->_M_node_allocator())
 	{
 	  _M_buckets = __ht._M_buckets;
-	  _M_before_begin()._M_nxt = __ht._M_before_begin()._M_nxt;
+	  _M_before_begin._M_nxt = __ht._M_before_begin._M_nxt;
 	  // Update, if necessary, bucket pointing to before begin that hasn't
 	  // moved.
 	  if (_M_begin())
-	    _M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin();
+	    _M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin;
 	  __ht._M_reset();
 	}
       else
@@ -1313,7 +1175,7 @@ 
 	  _M_assign(__ht,
 		    [this](__node_type* __n)
 		    {
-		      return _M_allocate_node(
+		      return this->_M_allocate_node(
 					std::move_if_noexcept(__n->_M_v()));
 		    });
 	  __ht.clear();
@@ -1341,27 +1203,27 @@ 
     _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
     swap(_Hashtable& __x)
-    noexcept(_Node_alloc_traits::_S_nothrow_swap())
+    noexcept(__node_alloc_traits::_S_nothrow_swap())
     {
       // The only base class with member variables is hash_code_base.
       // We define _Hash_code_base::_M_swap because different
       // specializations have different members.
       this->_M_swap(__x);
 
-      std::__alloc_on_swap(_M_node_allocator(), __x._M_node_allocator());
+      std::__alloc_on_swap(this->_M_node_allocator(), __x._M_node_allocator());
       std::swap(_M_rehash_policy, __x._M_rehash_policy);
       std::swap(_M_buckets, __x._M_buckets);
       std::swap(_M_bucket_count, __x._M_bucket_count);
-      std::swap(_M_before_begin()._M_nxt, __x._M_before_begin()._M_nxt);
+      std::swap(_M_before_begin._M_nxt, __x._M_before_begin._M_nxt);
       std::swap(_M_element_count, __x._M_element_count);
 
       // Fix buckets containing the _M_before_begin pointers that can't be
       // swapped.
       if (_M_begin())
-	_M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin();
+	_M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin;
       if (__x._M_begin())
 	__x._M_buckets[__x._M_bucket_index(__x._M_begin())]
-	  = &(__x._M_before_begin());
+	  = &__x._M_before_begin;
     }
 
   template<typename _Key, typename _Value,
@@ -1580,13 +1442,13 @@ 
 	  // The bucket is empty, the new node is inserted at the
 	  // beginning of the singly-linked list and the bucket will
 	  // contain _M_before_begin pointer.
-	  __node->_M_nxt = _M_before_begin()._M_nxt;
-	  _M_before_begin()._M_nxt = __node;
+	  __node->_M_nxt = _M_before_begin._M_nxt;
+	  _M_before_begin._M_nxt = __node;
 	  if (__node->_M_nxt)
 	    // We must update former begin bucket that is pointing to
 	    // _M_before_begin.
 	    _M_buckets[_M_bucket_index(__node->_M_next())] = __node;
-	  _M_buckets[__bkt] = &_M_before_begin();
+	  _M_buckets[__bkt] = &_M_before_begin;
 	}
     }
 
@@ -1608,8 +1470,8 @@ 
 	    _M_buckets[__next_bkt] = _M_buckets[__bkt];
 
 	  // Second update before begin node if necessary
-	  if (&_M_before_begin() == _M_buckets[__bkt])
-	    _M_before_begin()._M_nxt = __next;
+	  if (&_M_before_begin == _M_buckets[__bkt])
+	    _M_before_begin._M_nxt = __next;
 	  _M_buckets[__bkt] = nullptr;
 	}
     }
@@ -1645,7 +1507,7 @@ 
       _M_emplace(std::true_type, _Args&&... __args)
       {
 	// First build the node to get access to the hash code
-	__node_type* __node = _M_allocate_node(std::forward<_Args>(__args)...);
+	__node_type* __node = this->_M_allocate_node(std::forward<_Args>(__args)...);
 	const key_type& __k = this->_M_extract()(__node->_M_v());
 	__hash_code __code;
 	__try
@@ -1654,7 +1516,7 @@ 
 	  }
 	__catch(...)
 	  {
-	    _M_deallocate_node(__node);
+	    this->_M_deallocate_node(__node);
 	    __throw_exception_again;
 	  }
 
@@ -1662,7 +1524,7 @@ 
 	if (__node_type* __p = _M_find_node(__bkt, __k, __code))
 	  {
 	    // There is already an equivalent node, no insertion
-	    _M_deallocate_node(__node);
+	    this->_M_deallocate_node(__node);
 	    return std::make_pair(iterator(__p), false);
 	  }
 
@@ -1684,7 +1546,8 @@ 
       _M_emplace(const_iterator __hint, std::false_type, _Args&&... __args)
       {
 	// First build the node to get its hash code.
-	__node_type* __node = _M_allocate_node(std::forward<_Args>(__args)...);
+	__node_type* __node =
+	  this->_M_allocate_node(std::forward<_Args>(__args)...);
 
 	__hash_code __code;
 	__try
@@ -1693,7 +1556,7 @@ 
 	  }
 	__catch(...)
 	  {
-	    _M_deallocate_node(__node);
+	    this->_M_deallocate_node(__node);
 	    __throw_exception_again;
 	  }
 
@@ -1733,7 +1596,7 @@ 
 	}
       __catch(...)
 	{
-	  _M_deallocate_node(__node);
+	  this->_M_deallocate_node(__node);
 	  __throw_exception_again;
 	}
     }
@@ -1799,7 +1662,7 @@ 
 	}
       __catch(...)
 	{
-	  _M_deallocate_node(__node);
+	  this->_M_deallocate_node(__node);
 	  __throw_exception_again;
 	}
     }
@@ -1899,7 +1762,7 @@ 
 
       __prev_n->_M_nxt = __n->_M_nxt;
       iterator __result(__n->_M_next());
-      _M_deallocate_node(__n);
+      this->_M_deallocate_node(__n);
       --_M_element_count;
 
       return __result;
@@ -1972,7 +1835,7 @@ 
       do
 	{
 	  __node_type* __p = __n->_M_next();
-	  _M_deallocate_node(__n);
+	  this->_M_deallocate_node(__n);
 	  __n = __p;
 	  ++__result;
 	  --_M_element_count;
@@ -2014,7 +1877,7 @@ 
 	    {
 	      __node_type* __tmp = __n;
 	      __n = __n->_M_next();
-	      _M_deallocate_node(__tmp);
+	      this->_M_deallocate_node(__tmp);
 	      --_M_element_count;
 	      if (!__n)
 		break;
@@ -2044,10 +1907,10 @@ 
 	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
     clear() noexcept
     {
-      _M_deallocate_nodes(_M_begin());
+      this->_M_deallocate_nodes(_M_begin());
       __builtin_memset(_M_buckets, 0, _M_bucket_count * sizeof(__bucket_type));
       _M_element_count = 0;
-      _M_before_begin()._M_nxt = nullptr;
+      _M_before_begin._M_nxt = nullptr;
     }
 
   template<typename _Key, typename _Value,
@@ -2104,9 +1967,9 @@ 
 	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
     _M_rehash_aux(size_type __n, std::true_type)
     {
-      __bucket_type* __new_buckets = _M_allocate_buckets(__n);
+      __bucket_type* __new_buckets = this->_M_allocate_buckets(__n);
       __node_type* __p = _M_begin();
-      _M_before_begin()._M_nxt = nullptr;
+      _M_before_begin._M_nxt = nullptr;
       std::size_t __bbegin_bkt = 0;
       while (__p)
 	{
@@ -2114,9 +1977,9 @@ 
 	  std::size_t __bkt = __hash_code_base::_M_bucket_index(__p, __n);
 	  if (!__new_buckets[__bkt])
 	    {
-	      __p->_M_nxt = _M_before_begin()._M_nxt;
-	      _M_before_begin()._M_nxt = __p;
-	      __new_buckets[__bkt] = &_M_before_begin();
+	      __p->_M_nxt = _M_before_begin._M_nxt;
+	      _M_before_begin._M_nxt = __p;
+	      __new_buckets[__bkt] = &_M_before_begin;
 	      if (__p->_M_nxt)
 		__new_buckets[__bbegin_bkt] = __p;
 	      __bbegin_bkt = __bkt;
@@ -2146,10 +2009,10 @@ 
 	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
     _M_rehash_aux(size_type __n, std::false_type)
     {
-      __bucket_type* __new_buckets = _M_allocate_buckets(__n);
+      __bucket_type* __new_buckets = this->_M_allocate_buckets(__n);
 
       __node_type* __p = _M_begin();
-      _M_before_begin()._M_nxt = nullptr;
+      _M_before_begin._M_nxt = nullptr;
       std::size_t __bbegin_bkt = 0;
       std::size_t __prev_bkt = 0;
       __node_type* __prev_p = nullptr;
@@ -2194,9 +2057,9 @@ 
 
 	      if (!__new_buckets[__bkt])
 		{
-		  __p->_M_nxt = _M_before_begin()._M_nxt;
-		  _M_before_begin()._M_nxt = __p;
-		  __new_buckets[__bkt] = &_M_before_begin();
+		  __p->_M_nxt = _M_before_begin._M_nxt;
+		  _M_before_begin._M_nxt = __p;
+		  __new_buckets[__bkt] = &_M_before_begin;
 		  if (__p->_M_nxt)
 		    __new_buckets[__bbegin_bkt] = __p;
 		  __bbegin_bkt = __bkt;
Index: testsuite/23_containers/unordered_set/not_default_constructible_hash_neg.cc
===================================================================
--- testsuite/23_containers/unordered_set/not_default_constructible_hash_neg.cc	(revision 201521)
+++ testsuite/23_containers/unordered_set/not_default_constructible_hash_neg.cc	(working copy)
@@ -19,7 +19,7 @@ 
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-error "default constructible" "" { target *-*-* } 276 }
+// { dg-error "default constructible" "" { target *-*-* } 283 }
 
 #include <unordered_set>
 
Index: testsuite/23_containers/unordered_set/instantiation_neg.cc
===================================================================
--- testsuite/23_containers/unordered_set/instantiation_neg.cc	(revision 201521)
+++ testsuite/23_containers/unordered_set/instantiation_neg.cc	(working copy)
@@ -19,7 +19,7 @@ 
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-error "with noexcept" "" { target *-*-* } 258 }
+// { dg-error "with noexcept" "" { target *-*-* } 265 }
 
 #include <unordered_set>
 
Index: python/libstdcxx/v6/printers.py
===================================================================
--- python/libstdcxx/v6/printers.py	(revision 201521)
+++ python/libstdcxx/v6/printers.py	(working copy)
@@ -652,7 +652,7 @@ 
 
 class StdHashtableIterator:
     def __init__(self, hash):
-        self.node = hash['_M_bbegin']['_M_node']['_M_nxt']
+        self.node = hash['_M_before_begin']['_M_nxt']
         self.node_type = find_type(hash.type, '__node_type').pointer()
 
     def __iter__(self):