libstdc++-v3/include/bits/hashtable_policy.h

   1 // Internal policy header for unordered_set and unordered_map -*- C++ -*-
   2
   3 // Copyright (C) 2010-2013 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 bits/hashtable_policy.h
  26  *  This is an internal header file, included by other library headers.
  27  *  Do not attempt to use it directly.
  28  *  @headername{unordered_map,unordered_set}
  29  */
  30
  31 #ifndef _HASHTABLE_POLICY_H
  32 #define _HASHTABLE_POLICY_H 1
  33
  34 namespace std _GLIBCXX_VISIBILITY(default)
  35 {
  36 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  37
  38   template<typename _Key, typename _Value, typename _Alloc,
  39            typename _ExtractKey, typename _Equal,
  40            typename _H1, typename _H2, typename _Hash,
  41            typename _RehashPolicy, typename _Traits>
  42     class _Hashtable;
  43
  44 _GLIBCXX_END_NAMESPACE_VERSION
  45
  46 namespace __detail
  47 {
  48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  49
  50   /**
  51    *  @defgroup hashtable-detail Base and Implementation Classes
  52    *  @ingroup unordered_associative_containers
  53    *  @{
  54    */
  55   template<typename _Key, typename _Value,
  56            typename _ExtractKey, typename _Equal,
  57            typename _H1, typename _H2, typename _Hash, typename _Traits>
  58     struct _Hashtable_base;
  59
  60   // Helper function: return distance(first, last) for forward
  61   // iterators, or 0 for input iterators.
  62   template<class _Iterator>
  63     inline typename std::iterator_traits<_Iterator>::difference_type
  64     __distance_fw(_Iterator __first, _Iterator __last,
  65                   std::input_iterator_tag)
  66     { return 0; }
  67
  68   template<class _Iterator>
  69     inline typename std::iterator_traits<_Iterator>::difference_type
  70     __distance_fw(_Iterator __first, _Iterator __last,
  71                   std::forward_iterator_tag)
  72     { return std::distance(__first, __last); }
  73
  74   template<class _Iterator>
  75     inline typename std::iterator_traits<_Iterator>::difference_type
  76     __distance_fw(_Iterator __first, _Iterator __last)
  77     {
  78       typedef typename std::iterator_traits<_Iterator>::iterator_category _Tag;
  79       return __distance_fw(__first, __last, _Tag());
  80     }
  81
  82   // Helper type used to detect whether the hash functor is noexcept.
  83   template <typename _Key, typename _Hash>
  84     struct __is_noexcept_hash : std::integral_constant<bool,
  85         noexcept(declval<const _Hash&>()(declval<const _Key&>()))>
  86     { };
  87
  88   struct _Identity
  89   {
  90     template<typename _Tp>
  91       _Tp&&
  92       operator()(_Tp&& __x) const
  93       { return std::forward<_Tp>(__x); }
  94   };
  95
  96   struct _Select1st
  97   {
  98     template<typename _Tp>
  99       auto
 100       operator()(_Tp&& __x) const
 101       -> decltype(std::get<0>(std::forward<_Tp>(__x)))
 102       { return std::get<0>(std::forward<_Tp>(__x)); }
 103   };
 104
 105   template<typename _NodeAlloc>
 106     struct _Hashtable_alloc;
 107
 108   // Functor recycling a pool of nodes and using allocation once the pool is
 109   // empty.
 110   template<typename _NodeAlloc>
 111     struct _ReuseOrAllocNode
 112     {
 113     private:
 114       using __node_alloc_type = _NodeAlloc;
 115       using __hashtable_alloc = _Hashtable_alloc<__node_alloc_type>;
 116       using __value_alloc_type = typename __hashtable_alloc::__value_alloc_type;
 117       using __value_alloc_traits =
 118         typename __hashtable_alloc::__value_alloc_traits;
 119       using __node_alloc_traits =
 120         typename __hashtable_alloc::__node_alloc_traits;
 121       using __node_type = typename __hashtable_alloc::__node_type;
 122
 123     public:
 124       _ReuseOrAllocNode(__node_type* __nodes, __hashtable_alloc& __h)
 125         : _M_nodes(__nodes), _M_h(__h) { }
 126       _ReuseOrAllocNode(const _ReuseOrAllocNode&) = delete;
 127
 128       ~_ReuseOrAllocNode()
 129       { _M_h._M_deallocate_nodes(_M_nodes); }
 130
 131       template<typename _Arg>
 132         __node_type*
 133         operator()(_Arg&& __arg) const
 134         {
 135           if (_M_nodes)
 136             {
 137               __node_type* __node = _M_nodes;
 138               _M_nodes = _M_nodes->_M_next();
 139               __node->_M_nxt = nullptr;
 140               __value_alloc_type __a(_M_h._M_node_allocator());
 141               __value_alloc_traits::destroy(__a, __node->_M_valptr());
 142               __try
 143                 {
 144                   __value_alloc_traits::construct(__a, __node->_M_valptr(),
 145                                                   std::forward<_Arg>(__arg));
 146                 }
 147               __catch(...)
 148                 {
 149                   __node->~__node_type();
 150                   __node_alloc_traits::deallocate(_M_h._M_node_allocator(),
 151                                                   __node, 1);
 152                   __throw_exception_again;
 153                 }
 154               return __node;
 155             }
 156           return _M_h._M_allocate_node(std::forward<_Arg>(__arg));
 157         }
 158
 159     private:
 160       mutable __node_type* _M_nodes;
 161       __hashtable_alloc& _M_h;
 162     };
 163
 164   // Functor similar to the previous one but without any pool of node to recycle.
 165   template<typename _NodeAlloc>
 166     struct _AllocNode
 167     {
 168     private:
 169       using __hashtable_alloc = _Hashtable_alloc<_NodeAlloc>;
 170       using __node_type = typename __hashtable_alloc::__node_type;
 171
 172     public:
 173       _AllocNode(__hashtable_alloc& __h)
 174         : _M_h(__h) { }
 175
 176       template<typename _Arg>
 177         __node_type*
 178         operator()(_Arg&& __arg) const
 179         { return _M_h._M_allocate_node(std::forward<_Arg>(__arg)); }
 180
 181     private:
 182       __hashtable_alloc& _M_h;
 183     };
 184
 185   // Auxiliary types used for all instantiations of _Hashtable nodes
 186   // and iterators.
 187
 188   /**
 189    *  struct _Hashtable_traits
 190    *
 191    *  Important traits for hash tables.
 192    *
 193    *  @tparam _Cache_hash_code  Boolean value. True if the value of
 194    *  the hash function is stored along with the value. This is a
 195    *  time-space tradeoff.  Storing it may improve lookup speed by
 196    *  reducing the number of times we need to call the _Equal
 197    *  function.
 198    *
 199    *  @tparam _Constant_iterators  Boolean value. True if iterator and
 200    *  const_iterator are both constant iterator types. This is true
 201    *  for unordered_set and unordered_multiset, false for
 202    *  unordered_map and unordered_multimap.
 203    *
 204    *  @tparam _Unique_keys  Boolean value. True if the return value
 205    *  of _Hashtable::count(k) is always at most one, false if it may
 206    *  be an arbitrary number. This is true for unordered_set and
 207    *  unordered_map, false for unordered_multiset and
 208    *  unordered_multimap.
 209    */
 210   template<bool _Cache_hash_code, bool _Constant_iterators, bool _Unique_keys>
 211     struct _Hashtable_traits
 212     {
 213       template<bool _Cond>
 214         using __bool_constant = integral_constant<bool, _Cond>;
 215
 216       using __hash_cached = __bool_constant<_Cache_hash_code>;
 217       using __constant_iterators = __bool_constant<_Constant_iterators>;
 218       using __unique_keys = __bool_constant<_Unique_keys>;
 219     };
 220
 221   /**
 222    *  struct _Hash_node_base
 223    *
 224    *  Nodes, used to wrap elements stored in the hash table.  A policy
 225    *  template parameter of class template _Hashtable controls whether
 226    *  nodes also store a hash code. In some cases (e.g. strings) this
 227    *  may be a performance win.
 228    */
 229   struct _Hash_node_base
 230   {
 231     _Hash_node_base* _M_nxt;
 232
 233     _Hash_node_base() noexcept : _M_nxt() { }
 234
 235     _Hash_node_base(_Hash_node_base* __next) noexcept : _M_nxt(__next) { }
 236   };
 237
 238   /**
 239    *  struct _Hash_node_value_base
 240    *
 241    *  Node type with the value to store.
 242    */
 243   template<typename _Value>
 244     struct _Hash_node_value_base : _Hash_node_base
 245     {
 246       typedef _Value value_type;
 247
 248       __gnu_cxx::__aligned_buffer<_Value> _M_storage;
 249
 250       _Value*
 251       _M_valptr() noexcept
 252       { return _M_storage._M_ptr(); }
 253
 254       const _Value*
 255       _M_valptr() const noexcept
 256       { return _M_storage._M_ptr(); }
 257
 258       _Value&
 259       _M_v() noexcept
 260       { return *_M_valptr(); }
 261
 262       const _Value&
 263       _M_v() const noexcept
 264       { return *_M_valptr(); }
 265     };
 266
 267   /**
 268    *  Primary template struct _Hash_node.
 269    */
 270   template<typename _Value, bool _Cache_hash_code>
 271     struct _Hash_node;
 272
 273   /**
 274    *  Specialization for nodes with caches, struct _Hash_node.
 275    *
 276    *  Base class is __detail::_Hash_node_value_base.
 277    */
 278   template<typename _Value>
 279     struct _Hash_node<_Value, true> : _Hash_node_value_base<_Value>
 280     {
 281       std::size_t  _M_hash_code;
 282
 283       _Hash_node*
 284       _M_next() const noexcept
 285       { return static_cast<_Hash_node*>(this->_M_nxt); }
 286     };
 287
 288   /**
 289    *  Specialization for nodes without caches, struct _Hash_node.
 290    *
 291    *  Base class is __detail::_Hash_node_value_base.
 292    */
 293   template<typename _Value>
 294     struct _Hash_node<_Value, false> : _Hash_node_value_base<_Value>
 295     {
 296       _Hash_node*
 297       _M_next() const noexcept
 298       { return static_cast<_Hash_node*>(this->_M_nxt); }
 299     };
 300
 301   /// Base class for node iterators.
 302   template<typename _Value, bool _Cache_hash_code>
 303     struct _Node_iterator_base
 304     {
 305       using __node_type = _Hash_node<_Value, _Cache_hash_code>;
 306
 307       __node_type*  _M_cur;
 308
 309       _Node_iterator_base(__node_type* __p) noexcept
 310       : _M_cur(__p) { }
 311
 312       void
 313       _M_incr() noexcept
 314       { _M_cur = _M_cur->_M_next(); }
 315     };
 316
 317   template<typename _Value, bool _Cache_hash_code>
 318     inline bool
 319     operator==(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
 320                const _Node_iterator_base<_Value, _Cache_hash_code >& __y)
 321     noexcept
 322     { return __x._M_cur == __y._M_cur; }
 323
 324   template<typename _Value, bool _Cache_hash_code>
 325     inline bool
 326     operator!=(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
 327                const _Node_iterator_base<_Value, _Cache_hash_code>& __y)
 328     noexcept
 329     { return __x._M_cur != __y._M_cur; }
 330
 331   /// Node iterators, used to iterate through all the hashtable.
 332   template<typename _Value, bool __constant_iterators, bool __cache>
 333     struct _Node_iterator
 334     : public _Node_iterator_base<_Value, __cache>
 335     {
 336     private:
 337       using __base_type = _Node_iterator_base<_Value, __cache>;
 338       using __node_type = typename __base_type::__node_type;
 339
 340     public:
 341       typedef _Value                                    value_type;
 342       typedef std::ptrdiff_t                            difference_type;
 343       typedef std::forward_iterator_tag                 iterator_category;
 344
 345       using pointer = typename std::conditional<__constant_iterators,
 346                                                 const _Value*, _Value*>::type;
 347
 348       using reference = typename std::conditional<__constant_iterators,
 349                                                   const _Value&, _Value&>::type;
 350
 351       _Node_iterator() noexcept
 352       : __base_type(0) { }
 353
 354       explicit
 355       _Node_iterator(__node_type* __p) noexcept
 356       : __base_type(__p) { }
 357
 358       reference
 359       operator*() const noexcept
 360       { return this->_M_cur->_M_v(); }
 361
 362       pointer
 363       operator->() const noexcept
 364       { return this->_M_cur->_M_valptr(); }
 365
 366       _Node_iterator&
 367       operator++() noexcept
 368       {
 369         this->_M_incr();
 370         return *this;
 371       }
 372
 373       _Node_iterator
 374       operator++(int) noexcept
 375       {
 376         _Node_iterator __tmp(*this);
 377         this->_M_incr();
 378         return __tmp;
 379       }
 380     };
 381
 382   /// Node const_iterators, used to iterate through all the hashtable.
 383   template<typename _Value, bool __constant_iterators, bool __cache>
 384     struct _Node_const_iterator
 385     : public _Node_iterator_base<_Value, __cache>
 386     {
 387     private:
 388       using __base_type = _Node_iterator_base<_Value, __cache>;
 389       using __node_type = typename __base_type::__node_type;
 390
 391     public:
 392       typedef _Value                                    value_type;
 393       typedef std::ptrdiff_t                            difference_type;
 394       typedef std::forward_iterator_tag                 iterator_category;
 395
 396       typedef const _Value*                             pointer;
 397       typedef const _Value&                             reference;
 398
 399       _Node_const_iterator() noexcept
 400       : __base_type(0) { }
 401
 402       explicit
 403       _Node_const_iterator(__node_type* __p) noexcept
 404       : __base_type(__p) { }
 405
 406       _Node_const_iterator(const _Node_iterator<_Value, __constant_iterators,
 407                            __cache>& __x) noexcept
 408       : __base_type(__x._M_cur) { }
 409
 410       reference
 411       operator*() const noexcept
 412       { return this->_M_cur->_M_v(); }
 413
 414       pointer
 415       operator->() const noexcept
 416       { return this->_M_cur->_M_valptr(); }
 417
 418       _Node_const_iterator&
 419       operator++() noexcept
 420       {
 421         this->_M_incr();
 422         return *this;
 423       }
 424
 425       _Node_const_iterator
 426       operator++(int) noexcept
 427       {
 428         _Node_const_iterator __tmp(*this);
 429         this->_M_incr();
 430         return __tmp;
 431       }
 432     };
 433
 434   // Many of class template _Hashtable's template parameters are policy
 435   // classes.  These are defaults for the policies.
 436
 437   /// Default range hashing function: use division to fold a large number
 438   /// into the range [0, N).
 439   struct _Mod_range_hashing
 440   {
 441     typedef std::size_t first_argument_type;
 442     typedef std::size_t second_argument_type;
 443     typedef std::size_t result_type;
 444
 445     result_type
 446     operator()(first_argument_type __num,
 447                second_argument_type __den) const noexcept
 448     { return __num % __den; }
 449   };
 450
 451   /// Default ranged hash function H.  In principle it should be a
 452   /// function object composed from objects of type H1 and H2 such that
 453   /// h(k, N) = h2(h1(k), N), but that would mean making extra copies of
 454   /// h1 and h2.  So instead we'll just use a tag to tell class template
 455   /// hashtable to do that composition.
 456   struct _Default_ranged_hash { };
 457
 458   /// Default value for rehash policy.  Bucket size is (usually) the
 459   /// smallest prime that keeps the load factor small enough.
 460   struct _Prime_rehash_policy
 461   {
 462     _Prime_rehash_policy(float __z = 1.0)
 463     : _M_max_load_factor(__z), _M_next_resize(0) { }
 464
 465     float
 466     max_load_factor() const noexcept
 467     { return _M_max_load_factor; }
 468
 469     // Return a bucket size no smaller than n.
 470     std::size_t
 471     _M_next_bkt(std::size_t __n) const;
 472
 473     // Return a bucket count appropriate for n elements
 474     std::size_t
 475     _M_bkt_for_elements(std::size_t __n) const
 476     { return __builtin_ceil(__n / (long double)_M_max_load_factor); }
 477
 478     // __n_bkt is current bucket count, __n_elt is current element count,
 479     // and __n_ins is number of elements to be inserted.  Do we need to
 480     // increase bucket count?  If so, return make_pair(true, n), where n
 481     // is the new bucket count.  If not, return make_pair(false, 0).
 482     std::pair<bool, std::size_t>
 483     _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,
 484                    std::size_t __n_ins) const;
 485
 486     typedef std::size_t _State;
 487
 488     _State
 489     _M_state() const
 490     { return _M_next_resize; }
 491
 492     void
 493     _M_reset() noexcept
 494     { _M_next_resize = 0; }
 495
 496     void
 497     _M_reset(_State __state)
 498     { _M_next_resize = __state; }
 499
 500     enum { _S_n_primes = sizeof(unsigned long) != 8 ? 256 : 256 + 48 };
 501
 502     static const std::size_t _S_growth_factor = 2;
 503
 504     float               _M_max_load_factor;
 505     mutable std::size_t _M_next_resize;
 506   };
 507
 508   // Base classes for std::_Hashtable.  We define these base classes
 509   // because in some cases we want to do different things depending on
 510   // the value of a policy class.  In some cases the policy class
 511   // affects which member functions and nested typedefs are defined;
 512   // we handle that by specializing base class templates.  Several of
 513   // the base class templates need to access other members of class
 514   // template _Hashtable, so we use a variant of the "Curiously
 515   // Recurring Template Pattern" (CRTP) technique.
 516
 517   /**
 518    *  Primary class template _Map_base.
 519    *
 520    *  If the hashtable has a value type of the form pair<T1, T2> and a
 521    *  key extraction policy (_ExtractKey) that returns the first part
 522    *  of the pair, the hashtable gets a mapped_type typedef.  If it
 523    *  satisfies those criteria and also has unique keys, then it also
 524    *  gets an operator[].
 525    */
 526   template<typename _Key, typename _Value, typename _Alloc,
 527            typename _ExtractKey, typename _Equal,
 528            typename _H1, typename _H2, typename _Hash,
 529            typename _RehashPolicy, typename _Traits,
 530            bool _Unique_keys = _Traits::__unique_keys::value>
 531     struct _Map_base { };
 532
 533   /// Partial specialization, __unique_keys set to false.
 534   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 535            typename _H1, typename _H2, typename _Hash,
 536            typename _RehashPolicy, typename _Traits>
 537     struct _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 538                      _H1, _H2, _Hash, _RehashPolicy, _Traits, false>
 539     {
 540       using mapped_type = typename std::tuple_element<1, _Pair>::type;
 541     };
 542
 543   /// Partial specialization, __unique_keys set to true.
 544   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 545            typename _H1, typename _H2, typename _Hash,
 546            typename _RehashPolicy, typename _Traits>
 547     struct _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 548                      _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 549     {
 550     private:
 551       using __hashtable_base = __detail::_Hashtable_base<_Key, _Pair,
 552                                                          _Select1st,
 553                                                         _Equal, _H1, _H2, _Hash,
 554                                                           _Traits>;
 555
 556       using __hashtable = _Hashtable<_Key, _Pair, _Alloc,
 557                                      _Select1st, _Equal,
 558                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
 559
 560       using __hash_code = typename __hashtable_base::__hash_code;
 561       using __node_type = typename __hashtable_base::__node_type;
 562
 563     public:
 564       using key_type = typename __hashtable_base::key_type;
 565       using iterator = typename __hashtable_base::iterator;
 566       using mapped_type = typename std::tuple_element<1, _Pair>::type;
 567
 568       mapped_type&
 569       operator[](const key_type& __k);
 570
 571       mapped_type&
 572       operator[](key_type&& __k);
 573
 574       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 575       // DR 761. unordered_map needs an at() member function.
 576       mapped_type&
 577       at(const key_type& __k);
 578
 579       const mapped_type&
 580       at(const key_type& __k) const;
 581     };
 582
 583   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 584            typename _H1, typename _H2, typename _Hash,
 585            typename _RehashPolicy, typename _Traits>
 586     typename _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 587                        _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 588                        ::mapped_type&
 589     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 590               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 591     operator[](const key_type& __k)
 592     {
 593       __hashtable* __h = static_cast<__hashtable*>(this);
 594       __hash_code __code = __h->_M_hash_code(__k);
 595       std::size_t __n = __h->_M_bucket_index(__k, __code);
 596       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 597
 598       if (!__p)
 599         {
 600           __p = __h->_M_allocate_node(std::piecewise_construct,
 601                                       std::tuple<const key_type&>(__k),
 602                                       std::tuple<>());
 603           return __h->_M_insert_unique_node(__n, __code, __p)->second;
 604         }
 605
 606       return __p->_M_v().second;
 607     }
 608
 609   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 610            typename _H1, typename _H2, typename _Hash,
 611            typename _RehashPolicy, typename _Traits>
 612     typename _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 613                        _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 614                        ::mapped_type&
 615     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 616               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 617     operator[](key_type&& __k)
 618     {
 619       __hashtable* __h = static_cast<__hashtable*>(this);
 620       __hash_code __code = __h->_M_hash_code(__k);
 621       std::size_t __n = __h->_M_bucket_index(__k, __code);
 622       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 623
 624       if (!__p)
 625         {
 626           __p = __h->_M_allocate_node(std::piecewise_construct,
 627                                       std::forward_as_tuple(std::move(__k)),
 628                                       std::tuple<>());
 629           return __h->_M_insert_unique_node(__n, __code, __p)->second;
 630         }
 631
 632       return __p->_M_v().second;
 633     }
 634
 635   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 636            typename _H1, typename _H2, typename _Hash,
 637            typename _RehashPolicy, typename _Traits>
 638     typename _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 639                        _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 640                        ::mapped_type&
 641     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 642               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 643     at(const key_type& __k)
 644     {
 645       __hashtable* __h = static_cast<__hashtable*>(this);
 646       __hash_code __code = __h->_M_hash_code(__k);
 647       std::size_t __n = __h->_M_bucket_index(__k, __code);
 648       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 649
 650       if (!__p)
 651         __throw_out_of_range(__N("_Map_base::at"));
 652       return __p->_M_v().second;
 653     }
 654
 655   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 656            typename _H1, typename _H2, typename _Hash,
 657            typename _RehashPolicy, typename _Traits>
 658     const typename _Map_base<_Key, _Pair, _Alloc, _Select1st,
 659                              _Equal, _H1, _H2, _Hash, _RehashPolicy,
 660                              _Traits, true>::mapped_type&
 661     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 662               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 663     at(const key_type& __k) const
 664     {
 665       const __hashtable* __h = static_cast<const __hashtable*>(this);
 666       __hash_code __code = __h->_M_hash_code(__k);
 667       std::size_t __n = __h->_M_bucket_index(__k, __code);
 668       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 669
 670       if (!__p)
 671         __throw_out_of_range(__N("_Map_base::at"));
 672       return __p->_M_v().second;
 673     }
 674
 675   /**
 676    *  Primary class template _Insert_base.
 677    *
 678    *  insert member functions appropriate to all _Hashtables.
 679    */
 680   template<typename _Key, typename _Value, typename _Alloc,
 681            typename _ExtractKey, typename _Equal,
 682            typename _H1, typename _H2, typename _Hash,
 683            typename _RehashPolicy, typename _Traits>
 684     struct _Insert_base
 685     {
 686     protected:
 687       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 688                                      _Equal, _H1, _H2, _Hash,
 689                                      _RehashPolicy, _Traits>;
 690
 691       using __hashtable_base = _Hashtable_base<_Key, _Value, _ExtractKey,
 692                                                _Equal, _H1, _H2, _Hash,
 693                                                _Traits>;
 694
 695       using value_type = typename __hashtable_base::value_type;
 696       using iterator = typename __hashtable_base::iterator;
 697       using const_iterator =  typename __hashtable_base::const_iterator;
 698       using size_type = typename __hashtable_base::size_type;
 699
 700       using __unique_keys = typename __hashtable_base::__unique_keys;
 701       using __ireturn_type = typename __hashtable_base::__ireturn_type;
 702       using __node_type = _Hash_node<_Value, _Traits::__hash_cached::value>;
 703       using __node_alloc_type =
 704         typename __alloctr_rebind<_Alloc, __node_type>::__type;
 705       using __node_gen_type = _AllocNode<__node_alloc_type>;
 706
 707       __hashtable&
 708       _M_conjure_hashtable()
 709       { return *(static_cast<__hashtable*>(this)); }
 710
 711       template<typename _InputIterator, typename _NodeGetter>
 712         void
 713         _M_insert_range(_InputIterator __first, _InputIterator __last,
 714                         const _NodeGetter&);
 715
 716     public:
 717       __ireturn_type
 718       insert(const value_type& __v)
 719       {
 720         __hashtable& __h = _M_conjure_hashtable();
 721         __node_gen_type __node_gen(__h);
 722         return __h._M_insert(__v, __node_gen, __unique_keys());
 723       }
 724
 725       iterator
 726       insert(const_iterator __hint, const value_type& __v)
 727       {
 728         __hashtable& __h = _M_conjure_hashtable();
 729         __node_gen_type __node_gen(__h);
 730         return __h._M_insert(__hint, __v, __node_gen, __unique_keys());
 731       }
 732
 733       void
 734       insert(initializer_list<value_type> __l)
 735       { this->insert(__l.begin(), __l.end()); }
 736
 737       template<typename _InputIterator>
 738         void
 739         insert(_InputIterator __first, _InputIterator __last)
 740         {
 741           __hashtable& __h = _M_conjure_hashtable();
 742           __node_gen_type __node_gen(__h);
 743           return _M_insert_range(__first, __last, __node_gen);
 744         }
 745     };
 746
 747   template<typename _Key, typename _Value, typename _Alloc,
 748            typename _ExtractKey, typename _Equal,
 749            typename _H1, typename _H2, typename _Hash,
 750            typename _RehashPolicy, typename _Traits>
 751     template<typename _InputIterator, typename _NodeGetter>
 752       void
 753       _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 754                     _RehashPolicy, _Traits>::
 755       _M_insert_range(_InputIterator __first, _InputIterator __last,
 756                       const _NodeGetter& __node_gen)
 757       {
 758         using __rehash_type = typename __hashtable::__rehash_type;
 759         using __rehash_state = typename __hashtable::__rehash_state;
 760         using pair_type = std::pair<bool, std::size_t>;
 761
 762         size_type __n_elt = __detail::__distance_fw(__first, __last);
 763
 764         __hashtable& __h = _M_conjure_hashtable();
 765         __rehash_type& __rehash = __h._M_rehash_policy;
 766         const __rehash_state& __saved_state = __rehash._M_state();
 767         pair_type __do_rehash = __rehash._M_need_rehash(__h._M_bucket_count,
 768                                                         __h._M_element_count,
 769                                                         __n_elt);
 770
 771         if (__do_rehash.first)
 772           __h._M_rehash(__do_rehash.second, __saved_state);
 773
 774         for (; __first != __last; ++__first)
 775           __h._M_insert(*__first, __node_gen, __unique_keys());
 776       }
 777
 778   /**
 779    *  Primary class template _Insert.
 780    *
 781    *  Select insert member functions appropriate to _Hashtable policy choices.
 782    */
 783   template<typename _Key, typename _Value, typename _Alloc,
 784            typename _ExtractKey, typename _Equal,
 785            typename _H1, typename _H2, typename _Hash,
 786            typename _RehashPolicy, typename _Traits,
 787            bool _Constant_iterators = _Traits::__constant_iterators::value,
 788            bool _Unique_keys = _Traits::__unique_keys::value>
 789     struct _Insert;
 790
 791   /// Specialization.
 792   template<typename _Key, typename _Value, typename _Alloc,
 793            typename _ExtractKey, typename _Equal,
 794            typename _H1, typename _H2, typename _Hash,
 795            typename _RehashPolicy, typename _Traits>
 796     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 797                    _RehashPolicy, _Traits, true, true>
 798     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 799                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 800     {
 801       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 802                                         _Equal, _H1, _H2, _Hash,
 803                                         _RehashPolicy, _Traits>;
 804       using value_type = typename __base_type::value_type;
 805       using iterator = typename __base_type::iterator;
 806       using const_iterator =  typename __base_type::const_iterator;
 807
 808       using __unique_keys = typename __base_type::__unique_keys;
 809       using __hashtable = typename __base_type::__hashtable;
 810       using __node_gen_type = typename __base_type::__node_gen_type;
 811
 812       using __base_type::insert;
 813
 814       std::pair<iterator, bool>
 815       insert(value_type&& __v)
 816       {
 817         __hashtable& __h = this->_M_conjure_hashtable();
 818         __node_gen_type __node_gen(__h);
 819         return __h._M_insert(std::move(__v), __node_gen, __unique_keys());
 820       }
 821
 822       iterator
 823       insert(const_iterator __hint, value_type&& __v)
 824       {
 825         __hashtable& __h = this->_M_conjure_hashtable();
 826         __node_gen_type __node_gen(__h);
 827         return __h._M_insert(__hint, std::move(__v), __node_gen,
 828                              __unique_keys());
 829       }
 830     };
 831
 832   /// Specialization.
 833   template<typename _Key, typename _Value, typename _Alloc,
 834            typename _ExtractKey, typename _Equal,
 835            typename _H1, typename _H2, typename _Hash,
 836            typename _RehashPolicy, typename _Traits>
 837     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 838                    _RehashPolicy, _Traits, true, false>
 839     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 840                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 841     {
 842       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 843                                         _Equal, _H1, _H2, _Hash,
 844                                         _RehashPolicy, _Traits>;
 845       using value_type = typename __base_type::value_type;
 846       using iterator = typename __base_type::iterator;
 847       using const_iterator =  typename __base_type::const_iterator;
 848
 849       using __unique_keys = typename __base_type::__unique_keys;
 850       using __hashtable = typename __base_type::__hashtable;
 851       using __node_gen_type = typename __base_type::__node_gen_type;
 852
 853       using __base_type::insert;
 854
 855       iterator
 856       insert(value_type&& __v)
 857       {
 858         __hashtable& __h = this->_M_conjure_hashtable();
 859         __node_gen_type __node_gen(__h);
 860         return __h._M_insert(std::move(__v), __node_gen, __unique_keys());
 861       }
 862
 863       iterator
 864       insert(const_iterator __hint, value_type&& __v)
 865       {
 866         __hashtable& __h = this->_M_conjure_hashtable();
 867         __node_gen_type __node_gen(__h);
 868         return __h._M_insert(__hint, std::move(__v), __node_gen,
 869                              __unique_keys());
 870       }
 871     };
 872
 873   /// Specialization.
 874   template<typename _Key, typename _Value, typename _Alloc,
 875            typename _ExtractKey, typename _Equal,
 876            typename _H1, typename _H2, typename _Hash,
 877            typename _RehashPolicy, typename _Traits, bool _Unique_keys>
 878     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 879                    _RehashPolicy, _Traits, false, _Unique_keys>
 880     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 881                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 882     {
 883       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 884                                        _Equal, _H1, _H2, _Hash,
 885                                        _RehashPolicy, _Traits>;
 886       using value_type = typename __base_type::value_type;
 887       using iterator = typename __base_type::iterator;
 888       using const_iterator =  typename __base_type::const_iterator;
 889
 890       using __unique_keys = typename __base_type::__unique_keys;
 891       using __hashtable = typename __base_type::__hashtable;
 892       using __ireturn_type = typename __base_type::__ireturn_type;
 893
 894       using __base_type::insert;
 895
 896       template<typename _Pair>
 897         using __is_cons = std::is_constructible<value_type, _Pair&&>;
 898
 899       template<typename _Pair>
 900         using _IFcons = std::enable_if<__is_cons<_Pair>::value>;
 901
 902       template<typename _Pair>
 903         using _IFconsp = typename _IFcons<_Pair>::type;
 904
 905       template<typename _Pair, typename = _IFconsp<_Pair>>
 906         __ireturn_type
 907         insert(_Pair&& __v)
 908         {
 909           __hashtable& __h = this->_M_conjure_hashtable();
 910           return __h._M_emplace(__unique_keys(), std::forward<_Pair>(__v));
 911         }
 912
 913       template<typename _Pair, typename = _IFconsp<_Pair>>
 914         iterator
 915         insert(const_iterator __hint, _Pair&& __v)
 916         {
 917           __hashtable& __h = this->_M_conjure_hashtable();
 918           return __h._M_emplace(__hint, __unique_keys(),
 919                                 std::forward<_Pair>(__v));
 920         }
 921    };
 922
 923   /**
 924    *  Primary class template  _Rehash_base.
 925    *
 926    *  Give hashtable the max_load_factor functions and reserve iff the
 927    *  rehash policy is _Prime_rehash_policy.
 928   */
 929   template<typename _Key, typename _Value, typename _Alloc,
 930            typename _ExtractKey, typename _Equal,
 931            typename _H1, typename _H2, typename _Hash,
 932            typename _RehashPolicy, typename _Traits>
 933     struct _Rehash_base;
 934
 935   /// Specialization.
 936   template<typename _Key, typename _Value, typename _Alloc,
 937            typename _ExtractKey, typename _Equal,
 938            typename _H1, typename _H2, typename _Hash, typename _Traits>
 939     struct _Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 940                         _H1, _H2, _Hash, _Prime_rehash_policy, _Traits>
 941     {
 942       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 943                                      _Equal, _H1, _H2, _Hash,
 944                                      _Prime_rehash_policy, _Traits>;
 945
 946       float
 947       max_load_factor() const noexcept
 948       {
 949         const __hashtable* __this = static_cast<const __hashtable*>(this);
 950         return __this->__rehash_policy().max_load_factor();
 951       }
 952
 953       void
 954       max_load_factor(float __z)
 955       {
 956         __hashtable* __this = static_cast<__hashtable*>(this);
 957         __this->__rehash_policy(_Prime_rehash_policy(__z));
 958       }
 959
 960       void
 961       reserve(std::size_t __n)
 962       {
 963         __hashtable* __this = static_cast<__hashtable*>(this);
 964         __this->rehash(__builtin_ceil(__n / max_load_factor()));
 965       }
 966     };
 967
 968   /**
 969    *  Primary class template _Hashtable_ebo_helper.
 970    *
 971    *  Helper class using EBO when it is not forbidden (the type is not
 972    *  final) and when it is worth it (the type is empty.)
 973    */
 974   template<int _Nm, typename _Tp,
 975            bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
 976     struct _Hashtable_ebo_helper;
 977
 978   /// Specialization using EBO.
 979   template<int _Nm, typename _Tp>
 980     struct _Hashtable_ebo_helper<_Nm, _Tp, true>
 981     : private _Tp
 982     {
 983       _Hashtable_ebo_helper() = default;
 984
 985       template<typename _OtherTp>
 986         _Hashtable_ebo_helper(_OtherTp&& __tp)
 987           : _Tp(std::forward<_OtherTp>(__tp))
 988         { }
 989
 990       static const _Tp&
 991       _S_cget(const _Hashtable_ebo_helper& __eboh)
 992       { return static_cast<const _Tp&>(__eboh); }
 993
 994       static _Tp&
 995       _S_get(_Hashtable_ebo_helper& __eboh)
 996       { return static_cast<_Tp&>(__eboh); }
 997     };
 998
 999   /// Specialization not using EBO.
1000   template<int _Nm, typename _Tp>
1001     struct _Hashtable_ebo_helper<_Nm, _Tp, false>
1002     {
1003       _Hashtable_ebo_helper() = default;
1004
1005       template<typename _OtherTp>
1006         _Hashtable_ebo_helper(_OtherTp&& __tp)
1007           : _M_tp(std::forward<_OtherTp>(__tp))
1008         { }
1009
1010       static const _Tp&
1011       _S_cget(const _Hashtable_ebo_helper& __eboh)
1012       { return __eboh._M_tp; }
1013
1014       static _Tp&
1015       _S_get(_Hashtable_ebo_helper& __eboh)
1016       { return __eboh._M_tp; }
1017
1018     private:
1019       _Tp _M_tp;
1020     };
1021
1022   /**
1023    *  Primary class template _Local_iterator_base.
1024    *
1025    *  Base class for local iterators, used to iterate within a bucket
1026    *  but not between buckets.
1027    */
1028   template<typename _Key, typename _Value, typename _ExtractKey,
1029            typename _H1, typename _H2, typename _Hash,
1030            bool __cache_hash_code>
1031     struct _Local_iterator_base;
1032
1033   /**
1034    *  Primary class template _Hash_code_base.
1035    *
1036    *  Encapsulates two policy issues that aren't quite orthogonal.
1037    *   (1) the difference between using a ranged hash function and using
1038    *       the combination of a hash function and a range-hashing function.
1039    *       In the former case we don't have such things as hash codes, so
1040    *       we have a dummy type as placeholder.
1041    *   (2) Whether or not we cache hash codes.  Caching hash codes is
1042    *       meaningless if we have a ranged hash function.
1043    *
1044    *  We also put the key extraction objects here, for convenience.
1045    *  Each specialization derives from one or more of the template
1046    *  parameters to benefit from Ebo. This is important as this type
1047    *  is inherited in some cases by the _Local_iterator_base type used
1048    *  to implement local_iterator and const_local_iterator. As with
1049    *  any iterator type we prefer to make it as small as possible.
1050    *
1051    *  Primary template is unused except as a hook for specializations.
1052    */
1053   template<typename _Key, typename _Value, typename _ExtractKey,
1054            typename _H1, typename _H2, typename _Hash,
1055            bool __cache_hash_code>
1056     struct _Hash_code_base;
1057
1058   /// Specialization: ranged hash function, no caching hash codes.  H1
1059   /// and H2 are provided but ignored.  We define a dummy hash code type.
1060   template<typename _Key, typename _Value, typename _ExtractKey,
1061            typename _H1, typename _H2, typename _Hash>
1062     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash, false>
1063     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1064       private _Hashtable_ebo_helper<1, _Hash>
1065     {
1066     private:
1067       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1068       using __ebo_hash = _Hashtable_ebo_helper<1, _Hash>;
1069
1070     protected:
1071       typedef void*                                     __hash_code;
1072       typedef _Hash_node<_Value, false>                 __node_type;
1073
1074       // We need the default constructor for the local iterators.
1075       _Hash_code_base() = default;
1076
1077       _Hash_code_base(const _ExtractKey& __ex, const _H1&, const _H2&,
1078                       const _Hash& __h)
1079       : __ebo_extract_key(__ex), __ebo_hash(__h) { }
1080
1081       __hash_code
1082       _M_hash_code(const _Key& __key) const
1083       { return 0; }
1084
1085       std::size_t
1086       _M_bucket_index(const _Key& __k, __hash_code, std::size_t __n) const
1087       { return _M_ranged_hash()(__k, __n); }
1088
1089       std::size_t
1090       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1091         noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>(), (std::size_t)0)) )
1092       { return _M_ranged_hash()(_M_extract()(__p->_M_v()), __n); }
1093
1094       void
1095       _M_store_code(__node_type*, __hash_code) const
1096       { }
1097
1098       void
1099       _M_copy_code(__node_type*, const __node_type*) const
1100       { }
1101
1102       void
1103       _M_swap(_Hash_code_base& __x)
1104       {
1105         std::swap(_M_extract(), __x._M_extract());
1106         std::swap(_M_ranged_hash(), __x._M_ranged_hash());
1107       }
1108
1109       const _ExtractKey&
1110       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1111
1112       _ExtractKey&
1113       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1114
1115       const _Hash&
1116       _M_ranged_hash() const { return __ebo_hash::_S_cget(*this); }
1117
1118       _Hash&
1119       _M_ranged_hash() { return __ebo_hash::_S_get(*this); }
1120     };
1121
1122   // No specialization for ranged hash function while caching hash codes.
1123   // That combination is meaningless, and trying to do it is an error.
1124
1125   /// Specialization: ranged hash function, cache hash codes.  This
1126   /// combination is meaningless, so we provide only a declaration
1127   /// and no definition.
1128   template<typename _Key, typename _Value, typename _ExtractKey,
1129            typename _H1, typename _H2, typename _Hash>
1130     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash, true>;
1131
1132   /// Specialization: hash function and range-hashing function, no
1133   /// caching of hash codes.
1134   /// Provides typedef and accessor required by C++ 11.
1135   template<typename _Key, typename _Value, typename _ExtractKey,
1136            typename _H1, typename _H2>
1137     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2,
1138                            _Default_ranged_hash, false>
1139     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1140       private _Hashtable_ebo_helper<1, _H1>,
1141       private _Hashtable_ebo_helper<2, _H2>
1142     {
1143     private:
1144       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1145       using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>;
1146       using __ebo_h2 = _Hashtable_ebo_helper<2, _H2>;
1147
1148     public:
1149       typedef _H1                                       hasher;
1150
1151       hasher
1152       hash_function() const
1153       { return _M_h1(); }
1154
1155     protected:
1156       typedef std::size_t                               __hash_code;
1157       typedef _Hash_node<_Value, false>                 __node_type;
1158
1159       // We need the default constructor for the local iterators.
1160       _Hash_code_base() = default;
1161
1162       _Hash_code_base(const _ExtractKey& __ex,
1163                       const _H1& __h1, const _H2& __h2,
1164                       const _Default_ranged_hash&)
1165       : __ebo_extract_key(__ex), __ebo_h1(__h1), __ebo_h2(__h2) { }
1166
1167       __hash_code
1168       _M_hash_code(const _Key& __k) const
1169       { return _M_h1()(__k); }
1170
1171       std::size_t
1172       _M_bucket_index(const _Key&, __hash_code __c, std::size_t __n) const
1173       { return _M_h2()(__c, __n); }
1174
1175       std::size_t
1176       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1177         noexcept( noexcept(declval<const _H1&>()(declval<const _Key&>()))
1178                   && noexcept(declval<const _H2&>()((__hash_code)0, (std::size_t)0)) )
1179       { return _M_h2()(_M_h1()(_M_extract()(__p->_M_v())), __n); }
1180
1181       void
1182       _M_store_code(__node_type*, __hash_code) const
1183       { }
1184
1185       void
1186       _M_copy_code(__node_type*, const __node_type*) const
1187       { }
1188
1189       void
1190       _M_swap(_Hash_code_base& __x)
1191       {
1192         std::swap(_M_extract(), __x._M_extract());
1193         std::swap(_M_h1(), __x._M_h1());
1194         std::swap(_M_h2(), __x._M_h2());
1195       }
1196
1197       const _ExtractKey&
1198       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1199
1200       _ExtractKey&
1201       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1202
1203       const _H1&
1204       _M_h1() const { return __ebo_h1::_S_cget(*this); }
1205
1206       _H1&
1207       _M_h1() { return __ebo_h1::_S_get(*this); }
1208
1209       const _H2&
1210       _M_h2() const { return __ebo_h2::_S_cget(*this); }
1211
1212       _H2&
1213       _M_h2() { return __ebo_h2::_S_get(*this); }
1214     };
1215
1216   /// Specialization: hash function and range-hashing function,
1217   /// caching hash codes.  H is provided but ignored.  Provides
1218   /// typedef and accessor required by C++ 11.
1219   template<typename _Key, typename _Value, typename _ExtractKey,
1220            typename _H1, typename _H2>
1221     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2,
1222                            _Default_ranged_hash, true>
1223     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1224       private _Hashtable_ebo_helper<1, _H1>,
1225       private _Hashtable_ebo_helper<2, _H2>
1226     {
1227     private:
1228       // Gives access to _M_h2() to the local iterator implementation.
1229       friend struct _Local_iterator_base<_Key, _Value, _ExtractKey, _H1, _H2,
1230                                          _Default_ranged_hash, true>;
1231
1232       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1233       using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>;
1234       using __ebo_h2 = _Hashtable_ebo_helper<2, _H2>;
1235
1236     public:
1237       typedef _H1                                       hasher;
1238
1239       hasher
1240       hash_function() const
1241       { return _M_h1(); }
1242
1243     protected:
1244       typedef std::size_t                               __hash_code;
1245       typedef _Hash_node<_Value, true>                  __node_type;
1246
1247       _Hash_code_base(const _ExtractKey& __ex,
1248                       const _H1& __h1, const _H2& __h2,
1249                       const _Default_ranged_hash&)
1250       : __ebo_extract_key(__ex), __ebo_h1(__h1), __ebo_h2(__h2) { }
1251
1252       __hash_code
1253       _M_hash_code(const _Key& __k) const
1254       { return _M_h1()(__k); }
1255
1256       std::size_t
1257       _M_bucket_index(const _Key&, __hash_code __c,
1258                       std::size_t __n) const
1259       { return _M_h2()(__c, __n); }
1260
1261       std::size_t
1262       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1263         noexcept( noexcept(declval<const _H2&>()((__hash_code)0,
1264                                                  (std::size_t)0)) )
1265       { return _M_h2()(__p->_M_hash_code, __n); }
1266
1267       void
1268       _M_store_code(__node_type* __n, __hash_code __c) const
1269       { __n->_M_hash_code = __c; }
1270
1271       void
1272       _M_copy_code(__node_type* __to, const __node_type* __from) const
1273       { __to->_M_hash_code = __from->_M_hash_code; }
1274
1275       void
1276       _M_swap(_Hash_code_base& __x)
1277       {
1278         std::swap(_M_extract(), __x._M_extract());
1279         std::swap(_M_h1(), __x._M_h1());
1280         std::swap(_M_h2(), __x._M_h2());
1281       }
1282
1283       const _ExtractKey&
1284       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1285
1286       _ExtractKey&
1287       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1288
1289       const _H1&
1290       _M_h1() const { return __ebo_h1::_S_cget(*this); }
1291
1292       _H1&
1293       _M_h1() { return __ebo_h1::_S_get(*this); }
1294
1295       const _H2&
1296       _M_h2() const { return __ebo_h2::_S_cget(*this); }
1297
1298       _H2&
1299       _M_h2() { return __ebo_h2::_S_get(*this); }
1300     };
1301
1302   /**
1303    *  Primary class template _Equal_helper.
1304    *
1305    */
1306   template <typename _Key, typename _Value, typename _ExtractKey,
1307             typename _Equal, typename _HashCodeType,
1308             bool __cache_hash_code>
1309   struct _Equal_helper;
1310
1311   /// Specialization.
1312   template<typename _Key, typename _Value, typename _ExtractKey,
1313            typename _Equal, typename _HashCodeType>
1314   struct _Equal_helper<_Key, _Value, _ExtractKey, _Equal, _HashCodeType, true>
1315   {
1316     static bool
1317     _S_equals(const _Equal& __eq, const _ExtractKey& __extract,
1318               const _Key& __k, _HashCodeType __c, _Hash_node<_Value, true>* __n)
1319     { return __c == __n->_M_hash_code && __eq(__k, __extract(__n->_M_v())); }
1320   };
1321
1322   /// Specialization.
1323   template<typename _Key, typename _Value, typename _ExtractKey,
1324            typename _Equal, typename _HashCodeType>
1325   struct _Equal_helper<_Key, _Value, _ExtractKey, _Equal, _HashCodeType, false>
1326   {
1327     static bool
1328     _S_equals(const _Equal& __eq, const _ExtractKey& __extract,
1329               const _Key& __k, _HashCodeType, _Hash_node<_Value, false>* __n)
1330     { return __eq(__k, __extract(__n->_M_v())); }
1331   };
1332
1333
1334   /// Specialization.
1335   template<typename _Key, typename _Value, typename _ExtractKey,
1336            typename _H1, typename _H2, typename _Hash>
1337     struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1338                                 _H1, _H2, _Hash, true>
1339     : private _Hashtable_ebo_helper<0, _H2>
1340     {
1341     protected:
1342       using __base_type = _Hashtable_ebo_helper<0, _H2>;
1343       using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1344                                                _H1, _H2, _Hash, true>;
1345
1346     public:
1347       _Local_iterator_base() = default;
1348       _Local_iterator_base(const __hash_code_base& __base,
1349                            _Hash_node<_Value, true>* __p,
1350                            std::size_t __bkt, std::size_t __bkt_count)
1351       : __base_type(__base._M_h2()),
1352         _M_cur(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count) { }
1353
1354       void
1355       _M_incr()
1356       {
1357         _M_cur = _M_cur->_M_next();
1358         if (_M_cur)
1359           {
1360             std::size_t __bkt
1361               = __base_type::_S_get(*this)(_M_cur->_M_hash_code,
1362                                            _M_bucket_count);
1363             if (__bkt != _M_bucket)
1364               _M_cur = nullptr;
1365           }
1366       }
1367
1368       _Hash_node<_Value, true>*  _M_cur;
1369       std::size_t _M_bucket;
1370       std::size_t _M_bucket_count;
1371     };
1372
1373   /// Specialization.
1374   template<typename _Key, typename _Value, typename _ExtractKey,
1375            typename _H1, typename _H2, typename _Hash>
1376     struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1377                                 _H1, _H2, _Hash, false>
1378     : private _Hash_code_base<_Key, _Value, _ExtractKey,
1379                               _H1, _H2, _Hash, false>
1380     {
1381     protected:
1382       using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1383                                                _H1, _H2, _Hash, false>;
1384
1385     public:
1386       _Local_iterator_base() = default;
1387       _Local_iterator_base(const __hash_code_base& __base,
1388                            _Hash_node<_Value, false>* __p,
1389                            std::size_t __bkt, std::size_t __bkt_count)
1390         : __hash_code_base(__base),
1391           _M_cur(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count) { }
1392
1393       void
1394       _M_incr()
1395       {
1396         _M_cur = _M_cur->_M_next();
1397         if (_M_cur)
1398           {
1399             std::size_t __bkt = this->_M_bucket_index(_M_cur, _M_bucket_count);
1400             if (__bkt != _M_bucket)
1401               _M_cur = nullptr;
1402           }
1403       }
1404
1405       _Hash_node<_Value, false>*  _M_cur;
1406       std::size_t _M_bucket;
1407       std::size_t _M_bucket_count;
1408     };
1409
1410   template<typename _Key, typename _Value, typename _ExtractKey,
1411            typename _H1, typename _H2, typename _Hash, bool __cache>
1412     inline bool
1413     operator==(const _Local_iterator_base<_Key, _Value, _ExtractKey,
1414                                           _H1, _H2, _Hash, __cache>& __x,
1415                const _Local_iterator_base<_Key, _Value, _ExtractKey,
1416                                           _H1, _H2, _Hash, __cache>& __y)
1417     { return __x._M_cur == __y._M_cur; }
1418
1419   template<typename _Key, typename _Value, typename _ExtractKey,
1420            typename _H1, typename _H2, typename _Hash, bool __cache>
1421     inline bool
1422     operator!=(const _Local_iterator_base<_Key, _Value, _ExtractKey,
1423                                           _H1, _H2, _Hash, __cache>& __x,
1424                const _Local_iterator_base<_Key, _Value, _ExtractKey,
1425                                           _H1, _H2, _Hash, __cache>& __y)
1426     { return __x._M_cur != __y._M_cur; }
1427
1428   /// local iterators
1429   template<typename _Key, typename _Value, typename _ExtractKey,
1430            typename _H1, typename _H2, typename _Hash,
1431            bool __constant_iterators, bool __cache>
1432     struct _Local_iterator
1433     : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1434                                   _H1, _H2, _Hash, __cache>
1435     {
1436     private:
1437       using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1438                                                _H1, _H2, _Hash, __cache>;
1439       using __hash_code_base = typename __base_type::__hash_code_base;
1440     public:
1441       typedef _Value                                    value_type;
1442       typedef typename std::conditional<__constant_iterators,
1443                                         const _Value*, _Value*>::type
1444                                                        pointer;
1445       typedef typename std::conditional<__constant_iterators,
1446                                         const _Value&, _Value&>::type
1447                                                        reference;
1448       typedef std::ptrdiff_t                            difference_type;
1449       typedef std::forward_iterator_tag                 iterator_category;
1450
1451       _Local_iterator() = default;
1452
1453       _Local_iterator(const __hash_code_base& __base,
1454                       _Hash_node<_Value, __cache>* __p,
1455                       std::size_t __bkt, std::size_t __bkt_count)
1456         : __base_type(__base, __p, __bkt, __bkt_count)
1457       { }
1458
1459       reference
1460       operator*() const
1461       { return this->_M_cur->_M_v(); }
1462
1463       pointer
1464       operator->() const
1465       { return this->_M_cur->_M_valptr(); }
1466
1467       _Local_iterator&
1468       operator++()
1469       {
1470         this->_M_incr();
1471         return *this;
1472       }
1473
1474       _Local_iterator
1475       operator++(int)
1476       {
1477         _Local_iterator __tmp(*this);
1478         this->_M_incr();
1479         return __tmp;
1480       }
1481     };
1482
1483   /// local const_iterators
1484   template<typename _Key, typename _Value, typename _ExtractKey,
1485            typename _H1, typename _H2, typename _Hash,
1486            bool __constant_iterators, bool __cache>
1487     struct _Local_const_iterator
1488     : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1489                                   _H1, _H2, _Hash, __cache>
1490     {
1491     private:
1492       using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1493                                                _H1, _H2, _Hash, __cache>;
1494       using __hash_code_base = typename __base_type::__hash_code_base;
1495
1496     public:
1497       typedef _Value                                    value_type;
1498       typedef const _Value*                             pointer;
1499       typedef const _Value&                             reference;
1500       typedef std::ptrdiff_t                            difference_type;
1501       typedef std::forward_iterator_tag                 iterator_category;
1502
1503       _Local_const_iterator() = default;
1504
1505       _Local_const_iterator(const __hash_code_base& __base,
1506                             _Hash_node<_Value, __cache>* __p,
1507                             std::size_t __bkt, std::size_t __bkt_count)
1508         : __base_type(__base, __p, __bkt, __bkt_count)
1509       { }
1510
1511       _Local_const_iterator(const _Local_iterator<_Key, _Value, _ExtractKey,
1512                                                   _H1, _H2, _Hash,
1513                                                   __constant_iterators,
1514                                                   __cache>& __x)
1515         : __base_type(__x)
1516       { }
1517
1518       reference
1519       operator*() const
1520       { return this->_M_cur->_M_v(); }
1521
1522       pointer
1523       operator->() const
1524       { return this->_M_cur->_M_valptr(); }
1525
1526       _Local_const_iterator&
1527       operator++()
1528       {
1529         this->_M_incr();
1530         return *this;
1531       }
1532
1533       _Local_const_iterator
1534       operator++(int)
1535       {
1536         _Local_const_iterator __tmp(*this);
1537         this->_M_incr();
1538         return __tmp;
1539       }
1540     };
1541
1542   /**
1543    *  Primary class template _Hashtable_base.
1544    *
1545    *  Helper class adding management of _Equal functor to
1546    *  _Hash_code_base type.
1547    *
1548    *  Base class templates are:
1549    *    - __detail::_Hash_code_base
1550    *    - __detail::_Hashtable_ebo_helper
1551    */
1552   template<typename _Key, typename _Value,
1553            typename _ExtractKey, typename _Equal,
1554            typename _H1, typename _H2, typename _Hash, typename _Traits>
1555   struct _Hashtable_base
1556   : public _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash,
1557                            _Traits::__hash_cached::value>,
1558     private _Hashtable_ebo_helper<0, _Equal>
1559   {
1560   public:
1561     typedef _Key                                        key_type;
1562     typedef _Value                                      value_type;
1563     typedef _Equal                                      key_equal;
1564     typedef std::size_t                                 size_type;
1565     typedef std::ptrdiff_t                              difference_type;
1566
1567     using __traits_type = _Traits;
1568     using __hash_cached = typename __traits_type::__hash_cached;
1569     using __constant_iterators = typename __traits_type::__constant_iterators;
1570     using __unique_keys = typename __traits_type::__unique_keys;
1571
1572     using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1573                                              _H1, _H2, _Hash,
1574                                              __hash_cached::value>;
1575
1576     using __hash_code = typename __hash_code_base::__hash_code;
1577     using __node_type = typename __hash_code_base::__node_type;
1578
1579     using iterator = __detail::_Node_iterator<value_type,
1580                                               __constant_iterators::value,
1581                                               __hash_cached::value>;
1582
1583     using const_iterator = __detail::_Node_const_iterator<value_type,
1584                                                    __constant_iterators::value,
1585                                                    __hash_cached::value>;
1586
1587     using local_iterator = __detail::_Local_iterator<key_type, value_type,
1588                                                   _ExtractKey, _H1, _H2, _Hash,
1589                                                   __constant_iterators::value,
1590                                                      __hash_cached::value>;
1591
1592     using const_local_iterator = __detail::_Local_const_iterator<key_type,
1593                                                                  value_type,
1594                                         _ExtractKey, _H1, _H2, _Hash,
1595                                         __constant_iterators::value,
1596                                         __hash_cached::value>;
1597
1598     using __ireturn_type = typename std::conditional<__unique_keys::value,
1599                                                      std::pair<iterator, bool>,
1600                                                      iterator>::type;
1601   private:
1602     using _EqualEBO = _Hashtable_ebo_helper<0, _Equal>;
1603     using _EqualHelper =  _Equal_helper<_Key, _Value, _ExtractKey, _Equal,
1604                                         __hash_code, __hash_cached::value>;
1605
1606   protected:
1607     _Hashtable_base(const _ExtractKey& __ex, const _H1& __h1, const _H2& __h2,
1608                     const _Hash& __hash, const _Equal& __eq)
1609     : __hash_code_base(__ex, __h1, __h2, __hash), _EqualEBO(__eq)
1610     { }
1611
1612     bool
1613     _M_equals(const _Key& __k, __hash_code __c, __node_type* __n) const
1614     {
1615       return _EqualHelper::_S_equals(_M_eq(), this->_M_extract(),
1616                                      __k, __c, __n);
1617     }
1618
1619     void
1620     _M_swap(_Hashtable_base& __x)
1621     {
1622       __hash_code_base::_M_swap(__x);
1623       std::swap(_M_eq(), __x._M_eq());
1624     }
1625
1626     const _Equal&
1627     _M_eq() const { return _EqualEBO::_S_cget(*this); }
1628
1629     _Equal&
1630     _M_eq() { return _EqualEBO::_S_get(*this); }
1631   };
1632
1633   /**
1634    *  struct _Equality_base.
1635    *
1636    *  Common types and functions for class _Equality.
1637    */
1638   struct _Equality_base
1639   {
1640   protected:
1641     template<typename _Uiterator>
1642       static bool
1643       _S_is_permutation(_Uiterator, _Uiterator, _Uiterator);
1644   };
1645
1646   // See std::is_permutation in N3068.
1647   template<typename _Uiterator>
1648     bool
1649     _Equality_base::
1650     _S_is_permutation(_Uiterator __first1, _Uiterator __last1,
1651                       _Uiterator __first2)
1652     {
1653       for (; __first1 != __last1; ++__first1, ++__first2)
1654         if (!(*__first1 == *__first2))
1655           break;
1656
1657       if (__first1 == __last1)
1658         return true;
1659
1660       _Uiterator __last2 = __first2;
1661       std::advance(__last2, std::distance(__first1, __last1));
1662
1663       for (_Uiterator __it1 = __first1; __it1 != __last1; ++__it1)
1664         {
1665           _Uiterator __tmp =  __first1;
1666           while (__tmp != __it1 && !bool(*__tmp == *__it1))
1667             ++__tmp;
1668
1669           // We've seen this one before.
1670           if (__tmp != __it1)
1671             continue;
1672
1673           std::ptrdiff_t __n2 = 0;
1674           for (__tmp = __first2; __tmp != __last2; ++__tmp)
1675             if (*__tmp == *__it1)
1676               ++__n2;
1677
1678           if (!__n2)
1679             return false;
1680
1681           std::ptrdiff_t __n1 = 0;
1682           for (__tmp = __it1; __tmp != __last1; ++__tmp)
1683             if (*__tmp == *__it1)
1684               ++__n1;
1685
1686           if (__n1 != __n2)
1687             return false;
1688         }
1689       return true;
1690     }
1691
1692   /**
1693    *  Primary class template  _Equality.
1694    *
1695    *  This is for implementing equality comparison for unordered
1696    *  containers, per N3068, by John Lakos and Pablo Halpern.
1697    *  Algorithmically, we follow closely the reference implementations
1698    *  therein.
1699    */
1700   template<typename _Key, typename _Value, typename _Alloc,
1701            typename _ExtractKey, typename _Equal,
1702            typename _H1, typename _H2, typename _Hash,
1703            typename _RehashPolicy, typename _Traits,
1704            bool _Unique_keys = _Traits::__unique_keys::value>
1705     struct _Equality;
1706
1707   /// Specialization.
1708   template<typename _Key, typename _Value, typename _Alloc,
1709            typename _ExtractKey, typename _Equal,
1710            typename _H1, typename _H2, typename _Hash,
1711            typename _RehashPolicy, typename _Traits>
1712     struct _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1713                      _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
1714     {
1715       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1716                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
1717
1718       bool
1719       _M_equal(const __hashtable&) const;
1720     };
1721
1722   template<typename _Key, typename _Value, typename _Alloc,
1723            typename _ExtractKey, typename _Equal,
1724            typename _H1, typename _H2, typename _Hash,
1725            typename _RehashPolicy, typename _Traits>
1726     bool
1727     _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1728               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
1729     _M_equal(const __hashtable& __other) const
1730     {
1731       const __hashtable* __this = static_cast<const __hashtable*>(this);
1732
1733       if (__this->size() != __other.size())
1734         return false;
1735
1736       for (auto __itx = __this->begin(); __itx != __this->end(); ++__itx)
1737         {
1738           const auto __ity = __other.find(_ExtractKey()(*__itx));
1739           if (__ity == __other.end() || !bool(*__ity == *__itx))
1740             return false;
1741         }
1742       return true;
1743     }
1744
1745   /// Specialization.
1746   template<typename _Key, typename _Value, typename _Alloc,
1747            typename _ExtractKey, typename _Equal,
1748            typename _H1, typename _H2, typename _Hash,
1749            typename _RehashPolicy, typename _Traits>
1750     struct _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1751                      _H1, _H2, _Hash, _RehashPolicy, _Traits, false>
1752     : public _Equality_base
1753     {
1754       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1755                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
1756
1757       bool
1758       _M_equal(const __hashtable&) const;
1759     };
1760
1761   template<typename _Key, typename _Value, typename _Alloc,
1762            typename _ExtractKey, typename _Equal,
1763            typename _H1, typename _H2, typename _Hash,
1764            typename _RehashPolicy, typename _Traits>
1765     bool
1766     _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1767               _H1, _H2, _Hash, _RehashPolicy, _Traits, false>::
1768     _M_equal(const __hashtable& __other) const
1769     {
1770       const __hashtable* __this = static_cast<const __hashtable*>(this);
1771
1772       if (__this->size() != __other.size())
1773         return false;
1774
1775       for (auto __itx = __this->begin(); __itx != __this->end();)
1776         {
1777           const auto __xrange = __this->equal_range(_ExtractKey()(*__itx));
1778           const auto __yrange = __other.equal_range(_ExtractKey()(*__itx));
1779
1780           if (std::distance(__xrange.first, __xrange.second)
1781               != std::distance(__yrange.first, __yrange.second))
1782             return false;
1783
1784           if (!_S_is_permutation(__xrange.first, __xrange.second,
1785                                  __yrange.first))
1786             return false;
1787
1788           __itx = __xrange.second;
1789         }
1790       return true;
1791     }
1792
1793   /**
1794    * This type deals with all allocation and keeps an allocator instance through
1795    * inheritance to benefit from EBO when possible.
1796    */
1797   template<typename _NodeAlloc>
1798     struct _Hashtable_alloc : private _Hashtable_ebo_helper<0, _NodeAlloc>
1799     {
1800     private:
1801       using __ebo_node_alloc = _Hashtable_ebo_helper<0, _NodeAlloc>;
1802     public:
1803       using __node_type = typename _NodeAlloc::value_type;
1804       using __node_alloc_type = _NodeAlloc;
1805       // Use __gnu_cxx to benefit from _S_always_equal and al.
1806       using __node_alloc_traits = __gnu_cxx::__alloc_traits<__node_alloc_type>;
1807
1808       using __value_type = typename __node_type::value_type;
1809       using __value_alloc_type =
1810         typename __alloctr_rebind<__node_alloc_type, __value_type>::__type;
1811       using __value_alloc_traits = std::allocator_traits<__value_alloc_type>;
1812
1813       using __node_base = __detail::_Hash_node_base;
1814       using __bucket_type = __node_base*;
1815       using __bucket_alloc_type =
1816         typename __alloctr_rebind<__node_alloc_type, __bucket_type>::__type;
1817       using __bucket_alloc_traits = std::allocator_traits<__bucket_alloc_type>;
1818
1819       _Hashtable_alloc(const _Hashtable_alloc&) = default;
1820       _Hashtable_alloc(_Hashtable_alloc&&) = default;
1821
1822       template<typename _Alloc>
1823         _Hashtable_alloc(_Alloc&& __a)
1824           : __ebo_node_alloc(std::forward<_Alloc>(__a))
1825         { }
1826
1827       __node_alloc_type&
1828       _M_node_allocator()
1829       { return __ebo_node_alloc::_S_get(*this); }
1830
1831       const __node_alloc_type&
1832       _M_node_allocator() const
1833       { return __ebo_node_alloc::_S_cget(*this); }
1834
1835       template<typename... _Args>
1836         __node_type*
1837         _M_allocate_node(_Args&&... __args);
1838
1839       void
1840       _M_deallocate_node(__node_type* __n);
1841
1842       // Deallocate the linked list of nodes pointed to by __n
1843       void
1844       _M_deallocate_nodes(__node_type* __n);
1845
1846       __bucket_type*
1847       _M_allocate_buckets(std::size_t __n);
1848
1849       void
1850       _M_deallocate_buckets(__bucket_type*, std::size_t __n);
1851     };
1852
1853   // Definitions of class template _Hashtable_alloc's out-of-line member
1854   // functions.
1855   template<typename _NodeAlloc>
1856     template<typename... _Args>
1857       typename _Hashtable_alloc<_NodeAlloc>::__node_type*
1858       _Hashtable_alloc<_NodeAlloc>::_M_allocate_node(_Args&&... __args)
1859       {
1860         auto __nptr = __node_alloc_traits::allocate(_M_node_allocator(), 1);
1861         __node_type* __n = std::__addressof(*__nptr);
1862         __try
1863           {
1864             __value_alloc_type __a(_M_node_allocator());
1865             ::new ((void*)__n) __node_type();
1866             __value_alloc_traits::construct(__a, __n->_M_valptr(),
1867                                             std::forward<_Args>(__args)...);
1868             return __n;
1869           }
1870         __catch(...)
1871           {
1872             __node_alloc_traits::deallocate(_M_node_allocator(), __nptr, 1);
1873             __throw_exception_again;
1874           }
1875       }
1876
1877   template<typename _NodeAlloc>
1878     void
1879     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node(__node_type* __n)
1880     {
1881       typedef typename __node_alloc_traits::pointer _Ptr;
1882       auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__n);
1883       __value_alloc_type __a(_M_node_allocator());
1884       __value_alloc_traits::destroy(__a, __n->_M_valptr());
1885       __n->~__node_type();
1886       __node_alloc_traits::deallocate(_M_node_allocator(), __ptr, 1);
1887     }
1888
1889   template<typename _NodeAlloc>
1890     void
1891     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_nodes(__node_type* __n)
1892     {
1893       while (__n)
1894         {
1895           __node_type* __tmp = __n;
1896           __n = __n->_M_next();
1897           _M_deallocate_node(__tmp);
1898         }
1899     }
1900
1901   template<typename _NodeAlloc>
1902     typename _Hashtable_alloc<_NodeAlloc>::__bucket_type*
1903     _Hashtable_alloc<_NodeAlloc>::_M_allocate_buckets(std::size_t __n)
1904     {
1905       __bucket_alloc_type __alloc(_M_node_allocator());
1906
1907       auto __ptr = __bucket_alloc_traits::allocate(__alloc, __n);
1908       __bucket_type* __p = std::__addressof(*__ptr);
1909       __builtin_memset(__p, 0, __n * sizeof(__bucket_type));
1910       return __p;
1911     }
1912
1913   template<typename _NodeAlloc>
1914     void
1915     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_buckets(__bucket_type* __bkts,
1916                                                         std::size_t __n)
1917     {
1918       typedef typename __bucket_alloc_traits::pointer _Ptr;
1919       auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__bkts);
1920       __bucket_alloc_type __alloc(_M_node_allocator());
1921       __bucket_alloc_traits::deallocate(__alloc, __ptr, __n);
1922     }
1923
1924  //@} hashtable-detail
1925 _GLIBCXX_END_NAMESPACE_VERSION
1926 } // namespace __detail
1927 } // namespace std
1928
1929 #endif // _HASHTABLE_POLICY_H