gcc/libstdc++-v3/include/debug/unordered_map

// Debugging unordered_map/unordered_multimap implementation -*- C++ -*-

// Copyright (C) 2003-2026 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file debug/unordered_map
 *  This file is a GNU debug extension to the Standard C++ Library.
 */

#ifndef _GLIBCXX_DEBUG_UNORDERED_MAP
#define _GLIBCXX_DEBUG_UNORDERED_MAP 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else
# include <bits/c++config.h>
namespace std _GLIBCXX_VISIBILITY(default) { namespace __debug {
  template<typename _Key, typename _Tp, typename _Hash, typename _Pred,
	   typename _Allocator>
    class unordered_map;
  template<typename _Key, typename _Tp, typename _Hash, typename _Pred,
	   typename _Allocator>
    class unordered_multimap;
} } // namespace std::__debug

# include <unordered_map>

#include <debug/safe_unordered_container.h>
#include <debug/safe_container.h>
#include <debug/safe_iterator.h>
#include <debug/safe_local_iterator.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
namespace __debug
{
  /// Class std::unordered_map with safety/checking/debug instrumentation.
  template<typename _Key, typename _Tp,
	   typename _Hash = std::hash<_Key>,
	   typename _Pred = std::equal_to<_Key>,
	   typename _Alloc = std::allocator<std::pair<const _Key, _Tp> > >
    class unordered_map
    : public __gnu_debug::_Safe_container<
	unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>, _Alloc,
	__gnu_debug::_Safe_unordered_container>,
      public _GLIBCXX_STD_C::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>
    {
      typedef _GLIBCXX_STD_C::unordered_map<_Key, _Tp, _Hash,
					    _Pred, _Alloc>		_Base;
      typedef __gnu_debug::_Safe_container<unordered_map,
		   _Alloc, __gnu_debug::_Safe_unordered_container>	_Safe;
      typedef typename _Base::const_iterator	_Base_const_iterator;
      typedef typename _Base::iterator		_Base_iterator;
      typedef typename _Base::const_local_iterator
						_Base_const_local_iterator;
      typedef typename _Base::local_iterator	_Base_local_iterator;

      template<typename _ItT, typename _SeqT, typename _CatT>
	friend class ::__gnu_debug::_Safe_iterator;
      template<typename _ItT, typename _SeqT>
	friend class ::__gnu_debug::_Safe_local_iterator;

      // Reference wrapper for base class. See PR libstdc++/90102.
      struct _Base_ref
      {
	_Base_ref(const _Base& __r) : _M_ref(__r) { }

	const _Base& _M_ref;
      };

    public:
      typedef typename _Base::size_type			size_type;
      typedef typename _Base::hasher			hasher;
      typedef typename _Base::key_equal			key_equal;
      typedef typename _Base::allocator_type		allocator_type;

      typedef typename _Base::key_type			key_type;
      typedef typename _Base::value_type		value_type;
      typedef typename _Base::mapped_type		mapped_type;

      typedef typename _Base::pointer			pointer;
      typedef typename _Base::const_pointer		const_pointer;
      typedef typename _Base::reference			reference;
      typedef typename _Base::const_reference		const_reference;
      typedef __gnu_debug::_Safe_iterator<
	_Base_iterator, unordered_map>			iterator;
      typedef __gnu_debug::_Safe_iterator<
	_Base_const_iterator, unordered_map>		const_iterator;
      typedef __gnu_debug::_Safe_local_iterator<
	_Base_local_iterator, unordered_map>		local_iterator;
      typedef __gnu_debug::_Safe_local_iterator<
	_Base_const_local_iterator, unordered_map>	const_local_iterator;
      typedef typename _Base::difference_type		difference_type;

      unordered_map() = default;

      explicit
      unordered_map(size_type __n,
		    const hasher& __hf = hasher(),
		    const key_equal& __eql = key_equal(),
		    const allocator_type& __a = allocator_type())
      : _Base(__n, __hf, __eql, __a) { }

      template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      size_type __n = 0,
		      const hasher& __hf = hasher(),
		      const key_equal& __eql = key_equal(),
		      const allocator_type& __a = allocator_type())
	: _Base(__gnu_debug::__base(
		  __glibcxx_check_valid_constructor_range(__first, __last)),
		__gnu_debug::__base(__last), __n,
		__hf, __eql, __a) { }

      unordered_map(const unordered_map&) = default;

      unordered_map(_Base_ref __x)
      : _Base(__x._M_ref) { }

      unordered_map(unordered_map&&) = default;

      explicit
      unordered_map(const allocator_type& __a)
      : _Base(__a) { }

      unordered_map(const unordered_map& __umap,
		    const allocator_type& __a)
      : _Base(__umap, __a) { }

      unordered_map(unordered_map&& __umap,
		    const allocator_type& __a)
      noexcept( noexcept(_Base(std::move(__umap), __a)) )
      : _Safe(std::move(__umap), __a),
	_Base(std::move(__umap), __a) { }

      unordered_map(initializer_list<value_type> __l,
		    size_type __n = 0,
		    const hasher& __hf = hasher(),
		    const key_equal& __eql = key_equal(),
		    const allocator_type& __a = allocator_type())
      : _Base(__l, __n, __hf, __eql, __a) { }

      unordered_map(size_type __n, const allocator_type& __a)
      : unordered_map(__n, hasher(), key_equal(), __a)
      { }

      unordered_map(size_type __n,
		    const hasher& __hf,
		    const allocator_type& __a)
      : unordered_map(__n, __hf, key_equal(), __a)
      { }

      template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      const allocator_type& __a)
	: unordered_map(__first, __last, 0, hasher(), key_equal(), __a)
	{ }

      template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      size_type __n,
		      const allocator_type& __a)
	: unordered_map(__first, __last, __n, hasher(), key_equal(), __a)
	{ }

      template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      size_type __n,
		      const hasher& __hf,
		      const allocator_type& __a)
	: unordered_map(__first, __last, __n, __hf, key_equal(), __a)
	{ }

      unordered_map(initializer_list<value_type> __l,
		    const allocator_type& __a)
      : unordered_map(__l, 0, hasher(), key_equal(), __a)
      { }

      unordered_map(initializer_list<value_type> __l,
		    size_type __n,
		    const allocator_type& __a)
      : unordered_map(__l, __n, hasher(), key_equal(), __a)
      { }

      unordered_map(initializer_list<value_type> __l,
		    size_type __n,
		    const hasher& __hf,
		    const allocator_type& __a)
      : unordered_map(__l, __n, __hf, key_equal(), __a)
      { }

#if __glibcxx_containers_ranges // C++ >= 23
      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_map(from_range_t, _Rg&& __rg,
		      size_type __n = 0,
		      const hasher& __hf = hasher(),
		      const key_equal& __eql = key_equal(),
		      const allocator_type& __a = allocator_type())
	: _Base(from_range, std::forward<_Rg>(__rg), __n, __hf, __eql, __a)
        { }

      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_map(from_range_t, _Rg&& __rg, const allocator_type& __a)
	: _Base(from_range, std::forward<_Rg>(__rg), __a)
        { }

      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_map(from_range_t, _Rg&& __rg, size_type __n,
		      const allocator_type& __a)
	: _Base(from_range, std::forward<_Rg>(__rg), __n, __a)
        { }

      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_map(from_range_t, _Rg&& __rg, size_type __n,
		      const hasher& __hf, const allocator_type& __a)
	: _Base(from_range, std::forward<_Rg>(__rg), __n, __hf, __a)
        { }
#endif

      ~unordered_map() = default;

      unordered_map&
      operator=(const unordered_map&) = default;

      unordered_map&
      operator=(unordered_map&&) = default;

      unordered_map&
      operator=(initializer_list<value_type> __l)
      {
	_Base::operator=(__l);
	this->_M_invalidate_all();
	return *this;
      }

      using _Base::get_allocator;
      using _Base::empty;
      using _Base::size;
      using _Base::max_size;

      void
      swap(unordered_map& __x)
	noexcept( noexcept(declval<_Base&>().swap(__x)) )
      {
	_Safe::_M_swap(__x);
	_Base::swap(__x);
      }

      void
      clear() noexcept
      {
	_Base::clear();
	this->_M_invalidate_all();
      }

      iterator
      begin() noexcept
      { return { _Base::begin(), this }; }

      const_iterator
      begin() const noexcept
      { return { _Base::begin(), this }; }

      iterator
      end() noexcept
      { return { _Base::end(), this }; }

      const_iterator
      end() const noexcept
      { return { _Base::end(), this }; }

      const_iterator
      cbegin() const noexcept
      { return { _Base::cbegin(), this }; }

      const_iterator
      cend() const noexcept
      { return { _Base::cend(), this }; }

      // local versions
      local_iterator
      begin(size_type __b)
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::begin(__b), this };
      }

      local_iterator
      end(size_type __b)
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::end(__b), this };
      }

      const_local_iterator
      begin(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::begin(__b), this };
      }

      const_local_iterator
      end(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::end(__b), this };
      }

      const_local_iterator
      cbegin(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::cbegin(__b), this };
      }

      const_local_iterator
      cend(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::cend(__b), this };
      }

      using _Base::bucket_count;
      using _Base::max_bucket_count;
      using _Base::bucket;

      size_type
      bucket_size(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return _Base::bucket_size(__b);
      }

      using _Base::load_factor;

      float
      max_load_factor() const noexcept
      { return _Base::max_load_factor(); }

      void
      max_load_factor(float __f)
      {
	__glibcxx_check_max_load_factor(__f);
	_Base::max_load_factor(__f);
      }

      template<typename... _Args>
	std::pair<iterator, bool>
	emplace(_Args&&... __args)
	{
	  size_type __bucket_count = this->bucket_count();
	  auto __res = _Base::emplace(std::forward<_Args>(__args)...);
	  _M_check_rehashed(__bucket_count);
	  return { { __res.first, this }, __res.second };
	}

      template<typename... _Args>
	iterator
	emplace_hint(const_iterator __hint, _Args&&... __args)
	{
	  __glibcxx_check_insert(__hint);
	  size_type __bucket_count = this->bucket_count();
	  auto __it = _Base::emplace_hint(__hint.base(),
					  std::forward<_Args>(__args)...);
	  _M_check_rehashed(__bucket_count);
	  return { __it, this };
	}

      std::pair<iterator, bool>
      insert(const value_type& __obj)
      {
	size_type __bucket_count = this->bucket_count();
	auto __res = _Base::insert(__obj);
	_M_check_rehashed(__bucket_count);
	return { { __res.first, this }, __res.second };
      }

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2354. Unnecessary copying when inserting into maps with braced-init
      std::pair<iterator, bool>
      insert(value_type&& __x)
      {
	size_type __bucket_count = this->bucket_count();
	auto __res = _Base::insert(std::move(__x));
	_M_check_rehashed(__bucket_count);
	return { { __res.first, this }, __res.second };
      }

      template<typename _Pair, typename = typename
	       std::enable_if<std::is_constructible<value_type,
						    _Pair&&>::value>::type>
	std::pair<iterator, bool>
	insert(_Pair&& __obj)
	{
	  size_type __bucket_count = this->bucket_count();
	  auto __res = _Base::insert(std::forward<_Pair>(__obj));
	  _M_check_rehashed(__bucket_count);
	  return { { __res.first, this }, __res.second };
	}

      iterator
      insert(const_iterator __hint, const value_type& __obj)
      {
	__glibcxx_check_insert(__hint);
	size_type __bucket_count = this->bucket_count();
	auto __it = _Base::insert(__hint.base(), __obj);
	_M_check_rehashed(__bucket_count);
	return { __it, this };
      }

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2354. Unnecessary copying when inserting into maps with braced-init
      iterator
      insert(const_iterator __hint, value_type&& __x)
      {
	__glibcxx_check_insert(__hint);
	size_type __bucket_count = this->bucket_count();
	auto __it = _Base::insert(__hint.base(), std::move(__x));
	_M_check_rehashed(__bucket_count);
	return { __it, this };
      }

      template<typename _Pair, typename = typename
	       std::enable_if<std::is_constructible<value_type,
						    _Pair&&>::value>::type>
	iterator
	insert(const_iterator __hint, _Pair&& __obj)
	{
	  __glibcxx_check_insert(__hint);
	  size_type __bucket_count = this->bucket_count();
	  auto __it = _Base::insert(__hint.base(), std::forward<_Pair>(__obj));
	  _M_check_rehashed(__bucket_count);
	  return { __it, this };
	}

      void
      insert(std::initializer_list<value_type> __l)
      {
	size_type __bucket_count = this->bucket_count();
	_Base::insert(__l);
	_M_check_rehashed(__bucket_count);
      }

      template<typename _InputIterator>
	void
	insert(_InputIterator __first, _InputIterator __last)
	{
	  typename __gnu_debug::_Distance_traits<_InputIterator>::__type __dist;
	  __glibcxx_check_valid_range2(__first, __last, __dist);
	  size_type __bucket_count = this->bucket_count();

	  if (__dist.second >= __gnu_debug::__dp_sign)
	    _Base::insert(__gnu_debug::__unsafe(__first),
			  __gnu_debug::__unsafe(__last));
	  else
	    _Base::insert(__first, __last);

	  _M_check_rehashed(__bucket_count);
	}

#ifdef __glibcxx_unordered_map_try_emplace // C++ >= 17 && HOSTED
      template <typename... _Args>
	pair<iterator, bool>
	try_emplace(const key_type& __k, _Args&&... __args)
	{
	  auto __res = _Base::try_emplace(__k,
					  std::forward<_Args>(__args)...);
	  return { { __res.first, this }, __res.second };
	}

      template <typename... _Args>
	pair<iterator, bool>
	try_emplace(key_type&& __k, _Args&&... __args)
	{
	  auto __res = _Base::try_emplace(std::move(__k),
					  std::forward<_Args>(__args)...);
	  return { { __res.first, this }, __res.second };
	}

      template <typename... _Args>
	iterator
	try_emplace(const_iterator __hint, const key_type& __k,
		    _Args&&... __args)
	{
	  __glibcxx_check_insert(__hint);
	  return { _Base::try_emplace(__hint.base(), __k,
				      std::forward<_Args>(__args)...),
		   this };
	}

      template <typename... _Args>
	iterator
	try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args)
	{
	  __glibcxx_check_insert(__hint);
	  return { _Base::try_emplace(__hint.base(), std::move(__k),
				      std::forward<_Args>(__args)...),
		   this };
	}

      template <typename _Obj>
	pair<iterator, bool>
	insert_or_assign(const key_type& __k, _Obj&& __obj)
	{
	  auto __res = _Base::insert_or_assign(__k,
					       std::forward<_Obj>(__obj));
	  return { { __res.first, this }, __res.second };
	}

      template <typename _Obj>
	pair<iterator, bool>
	insert_or_assign(key_type&& __k, _Obj&& __obj)
	{
	  auto __res = _Base::insert_or_assign(std::move(__k),
					       std::forward<_Obj>(__obj));
	  return { { __res.first, this }, __res.second };
	}

      template <typename _Obj>
	iterator
	insert_or_assign(const_iterator __hint, const key_type& __k,
			 _Obj&& __obj)
	{
	  __glibcxx_check_insert(__hint);
	  return { _Base::insert_or_assign(__hint.base(), __k,
					   std::forward<_Obj>(__obj)),
		   this };
	}

      template <typename _Obj>
	iterator
	insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj)
	{
	  __glibcxx_check_insert(__hint);
	  return { _Base::insert_or_assign(__hint.base(), std::move(__k),
					   std::forward<_Obj>(__obj)),
		   this };
	}
#endif // C++17

#ifdef __glibcxx_node_extract // >= C++17 && HOSTED
      using node_type = typename _Base::node_type;
      using insert_return_type = _Node_insert_return<iterator, node_type>;

      node_type
      extract(const_iterator __position)
      {
	__glibcxx_check_erase(__position);
	return _M_extract(__position.base());
      }

      node_type
      extract(const key_type& __key)
      {
	const auto __position = _Base::find(__key);
	if (__position != _Base::end())
	  return _M_extract(__position);
	return {};
      }

# ifdef __glibcxx_associative_heterogeneous_erasure
      template <__heterogeneous_hash_key<unordered_map> _Kt>
	node_type
	extract(_Kt&& __key)
	{
	  const auto __position = _Base::find(__key);
	  if (__position != _Base::end())
	    return _M_extract(__position);
	  return {};
	}
#endif

      insert_return_type
      insert(node_type&& __nh)
      {
	auto __ret = _Base::insert(std::move(__nh));
	return
	  { { __ret.position, this }, __ret.inserted, std::move(__ret.node) };
      }

      iterator
      insert(const_iterator __hint, node_type&& __nh)
      {
	__glibcxx_check_insert(__hint);
	return { _Base::insert(__hint.base(), std::move(__nh)), this };
      }

      template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  auto __guard
	    = _Safe::_S_uc_guard(std::__detail::_Select1st{}, __source);
	  _Base::merge(__source);
	}

      template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }

      template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  auto __guard
	    = _Safe::_S_umc_guard(std::__detail::_Select1st{}, __source);
	  _Base::merge(__source);
	}

      template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }
#endif // C++17

      using _Base::hash_function;
      using _Base::key_eq;

      iterator
      find(const key_type& __key)
      { return { _Base::find(__key), this }; }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	iterator
	find(const _Kt& __k)
	{ return { _Base::find(__k), this }; }
#endif

      const_iterator
      find(const key_type& __key) const
      { return { _Base::find(__key), this }; }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	const_iterator
	find(const _Kt& __k) const
	{ return { _Base::find(__k), this }; }
#endif

      using _Base::count;
#if __cplusplus > 201703L
      using _Base::contains;
#endif

      std::pair<iterator, iterator>
      equal_range(const key_type& __key)
      {
	auto __res = _Base::equal_range(__key);
	return { { __res.first, this }, { __res.second, this } };
      }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	std::pair<iterator, iterator>
	equal_range(const _Kt& __k)
	{
	  auto __res = _Base::equal_range(__k);
	  return { { __res.first, this }, { __res.second, this } };
	}
#endif

      std::pair<const_iterator, const_iterator>
      equal_range(const key_type& __key) const
      {
	auto __res = _Base::equal_range(__key);
	return { { __res.first, this }, { __res.second, this } };
      }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	std::pair<const_iterator, const_iterator>
	equal_range(const _Kt& __k) const
	{
	  auto __res = _Base::equal_range(__k);
	  return { { __res.first, this }, { __res.second, this } };
	}
#endif

      using _Base::operator[];
      using _Base::at;

      size_type
      erase(const key_type& __key)
      {
	size_type __ret(0);
	auto __victim = _Base::find(__key);
	if (__victim != _Base::end())
	  {
	    _M_erase(__victim);
	    __ret = 1;
	  }
	return __ret;
      }

# ifdef __glibcxx_associative_heterogeneous_erasure
      template <__heterogeneous_hash_key<unordered_map> _Kt>
	size_type
	erase(_Kt&& __key)
	{
	  auto __victim = _Base::find(__key);
	  if (__victim != _Base::end())
	    return _M_erase(__victim), 1;
	  return 0;
	}
#endif

      iterator
      erase(const_iterator __it)
      {
	__glibcxx_check_erase(__it);
	return { _M_erase(__it.base()), this };
      }

      _Base_iterator
      erase(_Base_const_iterator __it)
      {
	__glibcxx_check_erase2(__it);
	return _M_erase(__it);
      }

      iterator
      erase(iterator __it)
      {
	__glibcxx_check_erase(__it);
	return { _M_erase(__it.base()), this };
      }

      iterator
      erase(const_iterator __first, const_iterator __last)
      {
	__glibcxx_check_erase_range(__first, __last);
	for (auto __tmp = __first.base(); __tmp != __last.base(); ++__tmp)
	  {
	    _GLIBCXX_DEBUG_VERIFY(__tmp != _Base::cend(),
				  _M_message(__gnu_debug::__msg_valid_range)
				  ._M_iterator(__first, "first")
				  ._M_iterator(__last, "last"));
	    _M_invalidate(__tmp);
	  }

	size_type __bucket_count = this->bucket_count();
	auto __next = _Base::erase(__first.base(), __last.base());
	_M_check_rehashed(__bucket_count);
	return { __next, this };
      }

      using _Base::rehash;
      using _Base::reserve;

      _Base&
      _M_base() noexcept	{ return *this; }

      const _Base&
      _M_base() const noexcept	{ return *this; }

    private:
      void
      _M_check_rehashed(size_type __prev_count)
      {
	if (__prev_count != this->bucket_count())
	  this->_M_invalidate_all();
      }

      void
      _M_invalidate(_Base_const_iterator __victim)
      {
	this->_M_invalidate_if(
	  [__victim](_Base_const_iterator __it) { return __it == __victim; });
	this->_M_invalidate_local_if(
	  [__victim](_Base_const_local_iterator __it)
	  { return __it == __victim; });
      }

      _Base_iterator
      _M_erase(_Base_const_iterator __victim)
      {
	_M_invalidate(__victim);
	size_type __bucket_count = this->bucket_count();
	_Base_iterator __next = _Base::erase(__victim);
	_M_check_rehashed(__bucket_count);
	return __next;
      }

#ifdef __glibcxx_node_extract // >= C++17 && HOSTED
      node_type
      _M_extract(_Base_const_iterator __victim)
      {
	_M_invalidate(__victim);
	return _Base::extract(__victim);
      }
#endif
    };

#if __cpp_deduction_guides >= 201606

  template<typename _InputIterator,
	   typename _Hash = hash<__iter_key_t<_InputIterator>>,
	   typename _Pred = equal_to<__iter_key_t<_InputIterator>>,
	   typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireNotAllocator<_Pred>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator,
		  typename unordered_map<int, int>::size_type = {},
		  _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>,
		     _Hash, _Pred, _Allocator>;

  template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
	   typename _Pred = equal_to<_Key>,
	   typename _Allocator = allocator<pair<const _Key, _Tp>>,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireNotAllocator<_Pred>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>,
		  typename unordered_map<int, int>::size_type = {},
		  _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
    -> unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>;

  template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator,
		  typename unordered_map<int, int>::size_type, _Allocator)
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>,
		     hash<__iter_key_t<_InputIterator>>,
		     equal_to<__iter_key_t<_InputIterator>>,
		     _Allocator>;

  template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator, _Allocator)
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>,
		     hash<__iter_key_t<_InputIterator>>,
		     equal_to<__iter_key_t<_InputIterator>>,
		     _Allocator>;

  template<typename _InputIterator, typename _Hash, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator,
		  typename unordered_map<int, int>::size_type,
		  _Hash, _Allocator)
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>, _Hash,
		     equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

  template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>,
		  typename unordered_map<int, int>::size_type,
		  _Allocator)
    -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

  template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>, _Allocator)
    -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

  template<typename _Key, typename _Tp, typename _Hash, typename _Allocator,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>,
		  typename unordered_map<int, int>::size_type,
		  _Hash, _Allocator)
    -> unordered_map<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;

#if __glibcxx_containers_ranges // C++ >= 23
  template<ranges::input_range _Rg,
	   __not_allocator_like _Hash = hash<__detail::__range_key_type<_Rg>>,
	   __not_allocator_like _Pred = equal_to<__detail::__range_key_type<_Rg>>,
	   __allocator_like _Allocator =
	     allocator<__detail::__range_to_alloc_type<_Rg>>>
    unordered_map(from_range_t, _Rg&&, unordered_map<int, int>::size_type = {},
		  _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
    -> unordered_map<__detail::__range_key_type<_Rg>,
		     __detail::__range_mapped_type<_Rg>,
		     _Hash, _Pred, _Allocator>;

  template<ranges::input_range _Rg,
	   __allocator_like _Allocator>
    unordered_map(from_range_t, _Rg&&, unordered_map<int, int>::size_type,
		  _Allocator)
    -> unordered_map<__detail::__range_key_type<_Rg>,
		     __detail::__range_mapped_type<_Rg>,
		     hash<__detail::__range_key_type<_Rg>>,
		     equal_to<__detail::__range_key_type<_Rg>>,
		     _Allocator>;

  template<ranges::input_range _Rg,
	   __allocator_like _Allocator>
    unordered_map(from_range_t, _Rg&&, _Allocator)
    -> unordered_map<__detail::__range_key_type<_Rg>,
		     __detail::__range_mapped_type<_Rg>,
		     hash<__detail::__range_key_type<_Rg>>,
		     equal_to<__detail::__range_key_type<_Rg>>,
		     _Allocator>;

  template<ranges::input_range _Rg,
	   __not_allocator_like _Hash,
	   __allocator_like _Allocator>
    unordered_map(from_range_t, _Rg&&, unordered_map<int, int>::size_type,
		  _Hash, _Allocator)
    -> unordered_map<__detail::__range_key_type<_Rg>,
		     __detail::__range_mapped_type<_Rg>,
		     _Hash, equal_to<__detail::__range_key_type<_Rg>>,
		     _Allocator>;
#endif
#endif

  template<typename _Key, typename _Tp, typename _Hash,
	   typename _Pred, typename _Alloc>
    inline void
    swap(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    noexcept(noexcept(__x.swap(__y)))
    { __x.swap(__y); }

  template<typename _Key, typename _Tp, typename _Hash,
	   typename _Pred, typename _Alloc>
    inline bool
    operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return __x._M_base() == __y._M_base(); }

#if __cpp_impl_three_way_comparison < 201907L
  template<typename _Key, typename _Tp, typename _Hash,
	   typename _Pred, typename _Alloc>
    inline bool
    operator!=(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return !(__x == __y); }
#endif

  /// Class std::unordered_multimap with safety/checking/debug instrumentation.
  template<typename _Key, typename _Tp,
	   typename _Hash = std::hash<_Key>,
	   typename _Pred = std::equal_to<_Key>,
	   typename _Alloc = std::allocator<std::pair<const _Key, _Tp> > >
    class unordered_multimap
      : public __gnu_debug::_Safe_container<
	unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>, _Alloc,
	__gnu_debug::_Safe_unordered_container>,
	public _GLIBCXX_STD_C::unordered_multimap<
	_Key, _Tp, _Hash, _Pred, _Alloc>
    {
      typedef _GLIBCXX_STD_C::unordered_multimap<_Key, _Tp, _Hash,
						 _Pred, _Alloc>		_Base;
      typedef __gnu_debug::_Safe_container<unordered_multimap,
	_Alloc, __gnu_debug::_Safe_unordered_container>			_Safe;
      typedef typename _Base::const_iterator	   _Base_const_iterator;
      typedef typename _Base::iterator		   _Base_iterator;
      typedef typename _Base::const_local_iterator _Base_const_local_iterator;
      typedef typename _Base::local_iterator	   _Base_local_iterator;

      template<typename _ItT, typename _SeqT, typename _CatT>
	friend class ::__gnu_debug::_Safe_iterator;
      template<typename _ItT, typename _SeqT>
	friend class ::__gnu_debug::_Safe_local_iterator;

      // Reference wrapper for base class. See PR libstdc++/90102.
      struct _Base_ref
      {
	_Base_ref(const _Base& __r) : _M_ref(__r) { }

	const _Base& _M_ref;
      };

    public:
      typedef typename _Base::size_type			size_type;
      typedef typename _Base::hasher			hasher;
      typedef typename _Base::key_equal			key_equal;
      typedef typename _Base::allocator_type		allocator_type;

      typedef typename _Base::key_type			key_type;
      typedef typename _Base::value_type		value_type;
      typedef typename _Base::mapped_type		mapped_type;

      typedef typename _Base::pointer			pointer;
      typedef typename _Base::const_pointer		const_pointer;
      typedef typename _Base::reference			reference;
      typedef typename _Base::const_reference		const_reference;
      typedef __gnu_debug::_Safe_iterator<
	_Base_iterator, unordered_multimap>		iterator;
      typedef __gnu_debug::_Safe_iterator<
	_Base_const_iterator, unordered_multimap>	const_iterator;
      typedef __gnu_debug::_Safe_local_iterator<
	_Base_local_iterator, unordered_multimap>	local_iterator;
      typedef __gnu_debug::_Safe_local_iterator<
	_Base_const_local_iterator, unordered_multimap>	const_local_iterator;
      typedef typename _Base::difference_type		difference_type;

      unordered_multimap() = default;

      explicit
      unordered_multimap(size_type __n,
			 const hasher& __hf = hasher(),
			 const key_equal& __eql = key_equal(),
			 const allocator_type& __a = allocator_type())
      : _Base(__n, __hf, __eql, __a) { }

      template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   size_type __n = 0,
			   const hasher& __hf = hasher(),
			   const key_equal& __eql = key_equal(),
			   const allocator_type& __a = allocator_type())
	: _Base(__gnu_debug::__base(
		  __glibcxx_check_valid_constructor_range(__first, __last)),
		__gnu_debug::__base(__last), __n,
		__hf, __eql, __a) { }

      unordered_multimap(const unordered_multimap&) = default;

      unordered_multimap(_Base_ref __x)
      : _Base(__x._M_ref) { }

      unordered_multimap(unordered_multimap&&) = default;

      explicit
      unordered_multimap(const allocator_type& __a)
      : _Base(__a) { }

      unordered_multimap(const unordered_multimap& __umap,
			 const allocator_type& __a)
      : _Base(__umap, __a) { }

      unordered_multimap(unordered_multimap&& __umap,
			 const allocator_type& __a)
      noexcept( noexcept(_Base(std::move(__umap), __a)) )
      : _Safe(std::move(__umap), __a),
	_Base(std::move(__umap), __a) { }

      unordered_multimap(initializer_list<value_type> __l,
			 size_type __n = 0,
			 const hasher& __hf = hasher(),
			 const key_equal& __eql = key_equal(),
			 const allocator_type& __a = allocator_type())
      : _Base(__l, __n, __hf, __eql, __a) { }

      unordered_multimap(size_type __n, const allocator_type& __a)
      : unordered_multimap(__n, hasher(), key_equal(), __a)
      { }

      unordered_multimap(size_type __n, const hasher& __hf,
			 const allocator_type& __a)
      : unordered_multimap(__n, __hf, key_equal(), __a)
      { }

      template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   const allocator_type& __a)
	: unordered_multimap(__first, __last, 0, hasher(), key_equal(), __a)
	{ }

      template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   size_type __n,
			   const allocator_type& __a)
	: unordered_multimap(__first, __last, __n, hasher(), key_equal(), __a)
	{ }

      template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   size_type __n, const hasher& __hf,
			   const allocator_type& __a)
	: unordered_multimap(__first, __last, __n, __hf, key_equal(), __a)
	{ }

      unordered_multimap(initializer_list<value_type> __l,
			 const allocator_type& __a)
      : unordered_multimap(__l, 0, hasher(), key_equal(), __a)
      { }

      unordered_multimap(initializer_list<value_type> __l,
			 size_type __n,
			 const allocator_type& __a)
      : unordered_multimap(__l, __n, hasher(), key_equal(), __a)
      { }

      unordered_multimap(initializer_list<value_type> __l,
			 size_type __n, const hasher& __hf,
			 const allocator_type& __a)
      : unordered_multimap(__l, __n, __hf, key_equal(), __a)
      { }

#if __glibcxx_containers_ranges // C++ >= 23
      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_multimap(from_range_t, _Rg&& __rg,
		           size_type __n = 0,
		           const hasher& __hf = hasher(),
		           const key_equal& __eql = key_equal(),
		           const allocator_type& __a = allocator_type())
	: _Base(from_range, std::forward<_Rg>(__rg), __n, __hf, __eql, __a)
        { }

      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_multimap(from_range_t, _Rg&& __rg, const allocator_type& __a)
	: _Base(from_range, std::forward<_Rg>(__rg), __a)
        { }

      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_multimap(from_range_t, _Rg&& __rg, size_type __n,
		           const allocator_type& __a)
	: _Base(from_range, std::forward<_Rg>(__rg), __n, __a)
        { }

      template<__detail::__container_compatible_range<value_type> _Rg>
	unordered_multimap(from_range_t, _Rg&& __rg, size_type __n,
		           const hasher& __hf, const allocator_type& __a)
	: _Base(from_range, std::forward<_Rg>(__rg), __n, __hf, __a)
        { }
#endif

      ~unordered_multimap() = default;

      unordered_multimap&
      operator=(const unordered_multimap&) = default;

      unordered_multimap&
      operator=(unordered_multimap&&) = default;

      unordered_multimap&
      operator=(initializer_list<value_type> __l)
      {
	_Base::operator=(__l);
	this->_M_invalidate_all();
	return *this;
      }

      using _Base::get_allocator;
      using _Base::empty;
      using _Base::size;
      using _Base::max_size;

      void
      swap(unordered_multimap& __x)
	noexcept( noexcept(declval<_Base&>().swap(__x)) )
      {
	_Safe::_M_swap(__x);
	_Base::swap(__x);
      }

      void
      clear() noexcept
      {
	_Base::clear();
	this->_M_invalidate_all();
      }

      iterator
      begin() noexcept
      { return { _Base::begin(), this }; }

      const_iterator
      begin() const noexcept
      { return { _Base::begin(), this }; }

      iterator
      end() noexcept
      { return { _Base::end(), this }; }

      const_iterator
      end() const noexcept
      { return { _Base::end(), this }; }

      const_iterator
      cbegin() const noexcept
      { return { _Base::cbegin(), this }; }

      const_iterator
      cend() const noexcept
      { return { _Base::cend(), this }; }

      // local versions
      local_iterator
      begin(size_type __b)
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::begin(__b), this };
      }

      local_iterator
      end(size_type __b)
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::end(__b), this };
      }

      const_local_iterator
      begin(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::begin(__b), this };
      }

      const_local_iterator
      end(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::end(__b), this };
      }

      const_local_iterator
      cbegin(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::cbegin(__b), this };
      }

      const_local_iterator
      cend(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return { _Base::cend(__b), this };
      }

      using _Base::bucket_count;
      using _Base::max_bucket_count;
      using _Base::bucket;

      size_type
      bucket_size(size_type __b) const
      {
	__glibcxx_check_bucket_index(__b);
	return _Base::bucket_size(__b);
      }

      float
      max_load_factor() const noexcept
      { return _Base::max_load_factor(); }

      void
      max_load_factor(float __f)
      {
	__glibcxx_check_max_load_factor(__f);
	_Base::max_load_factor(__f);
      }

      template<typename... _Args>
	iterator
	emplace(_Args&&... __args)
	{
	  size_type __bucket_count = this->bucket_count();
	  auto __it = _Base::emplace(std::forward<_Args>(__args)...);
	  _M_check_rehashed(__bucket_count);
	  return { __it, this };
	}

      template<typename... _Args>
	iterator
	emplace_hint(const_iterator __hint, _Args&&... __args)
	{
	  __glibcxx_check_insert(__hint);
	  size_type __bucket_count = this->bucket_count();
	  auto __it = _Base::emplace_hint(__hint.base(),
					  std::forward<_Args>(__args)...);
	  _M_check_rehashed(__bucket_count);
	  return { __it, this };
	}

      iterator
      insert(const value_type& __obj)
      {
	size_type __bucket_count = this->bucket_count();
	auto __it = _Base::insert(__obj);
	_M_check_rehashed(__bucket_count);
	return { __it, this };
      }

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2354. Unnecessary copying when inserting into maps with braced-init
      iterator
      insert(value_type&& __x)
      {
	size_type __bucket_count = this->bucket_count();
	auto __it = _Base::insert(std::move(__x));
	_M_check_rehashed(__bucket_count);
	return { __it, this };
      }

      iterator
      insert(const_iterator __hint, const value_type& __obj)
      {
	__glibcxx_check_insert(__hint);
	size_type __bucket_count = this->bucket_count();
	auto __it = _Base::insert(__hint.base(), __obj);
	_M_check_rehashed(__bucket_count);
	return { __it, this };
      }

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2354. Unnecessary copying when inserting into maps with braced-init
      iterator
      insert(const_iterator __hint, value_type&& __x)
      {
	__glibcxx_check_insert(__hint);
	size_type __bucket_count = this->bucket_count();
	auto __it = _Base::insert(__hint.base(), std::move(__x));
	_M_check_rehashed(__bucket_count);
	return { __it, this };
      }

      template<typename _Pair, typename = typename
	       std::enable_if<std::is_constructible<value_type,
						    _Pair&&>::value>::type>
	iterator
	insert(_Pair&& __obj)
	{
	  size_type __bucket_count = this->bucket_count();
	  auto __it = _Base::insert(std::forward<_Pair>(__obj));
	  _M_check_rehashed(__bucket_count);
	  return { __it, this };
	}

      template<typename _Pair, typename = typename
	       std::enable_if<std::is_constructible<value_type,
						    _Pair&&>::value>::type>
	iterator
	insert(const_iterator __hint, _Pair&& __obj)
	{
	  __glibcxx_check_insert(__hint);
	  size_type __bucket_count = this->bucket_count();
	  auto __it = _Base::insert(__hint.base(), std::forward<_Pair>(__obj));
	  _M_check_rehashed(__bucket_count);
	  return { __it, this };
	}

      void
      insert(std::initializer_list<value_type> __l)
      { _Base::insert(__l); }

      template<typename _InputIterator>
	void
	insert(_InputIterator __first, _InputIterator __last)
	{
	  typename __gnu_debug::_Distance_traits<_InputIterator>::__type __dist;
	  __glibcxx_check_valid_range2(__first, __last, __dist);
	  size_type __bucket_count = this->bucket_count();

	  if (__dist.second >= __gnu_debug::__dp_sign)
	    _Base::insert(__gnu_debug::__unsafe(__first),
			  __gnu_debug::__unsafe(__last));
	  else
	    _Base::insert(__first, __last);

	  _M_check_rehashed(__bucket_count);
	}

#ifdef __glibcxx_node_extract // >= C++17 && HOSTED
      using node_type = typename _Base::node_type;

      node_type
      extract(const_iterator __position)
      {
	__glibcxx_check_erase(__position);
	return _M_extract(__position.base());
      }

      node_type
      extract(const key_type& __key)
      {
	const auto __position = _Base::find(__key);
	if (__position != _Base::end())
	  return _M_extract(__position);
	return {};
      }

# ifdef __glibcxx_associative_heterogeneous_erasure
      template <__heterogeneous_hash_key<unordered_multimap> _Kt>
	node_type
	extract(_Kt&& __key)
	{
	  const auto __position = _Base::find(__key);
	  if (__position != _Base::end())
	    return _M_extract(__position);
	  return {};
	}
#endif

      iterator
      insert(node_type&& __nh)
      { return { _Base::insert(std::move(__nh)), this }; }

      iterator
      insert(const_iterator __hint, node_type&& __nh)
      {
	__glibcxx_check_insert(__hint);
	return { _Base::insert(__hint.base(), std::move(__nh)), this };
      }

      template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  auto __guard
	    = _Safe::_S_umc_guard(std::__detail::_Select1st{}, __source);
	  _Base::merge(__source);
	}

      template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }

      template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  auto __guard
	    = _Safe::_S_uc_guard(std::__detail::_Select1st{}, __source);
	  _Base::merge(__source);
	}

      template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }
#endif // C++17

      using _Base::hash_function;
      using _Base::key_eq;

      iterator
      find(const key_type& __key)
      { return { _Base::find(__key), this }; }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	iterator
	find(const _Kt& __k)
	{ return { _Base::find(__k), this }; }
#endif

      const_iterator
      find(const key_type& __key) const
      { return { _Base::find(__key), this }; }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	const_iterator
	find(const _Kt& __k) const
	{ return { _Base::find(__k), this }; }
#endif

      using _Base::count;
#if __cplusplus > 201703L
      using _Base::contains;
#endif

      std::pair<iterator, iterator>
      equal_range(const key_type& __key)
      {
	auto __res = _Base::equal_range(__key);
	return { { __res.first, this }, { __res.second, this } };
      }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	std::pair<iterator, iterator>
	equal_range(const _Kt& __k)
	{
	  auto __res = _Base::equal_range(__k);
	  return { { __res.first, this }, { __res.second, this } };
	}
#endif

      std::pair<const_iterator, const_iterator>
      equal_range(const key_type& __key) const
      {
	auto __res = _Base::equal_range(__key);
	return { { __res.first, this }, { __res.second, this } };
      }

#ifdef __glibcxx_generic_unordered_lookup // C++ >= 20 && HOSTED
      template<typename _Kt,
	       typename = std::__has_is_transparent_t<_Hash, _Kt>,
	       typename = std::__has_is_transparent_t<_Pred, _Kt>>
	std::pair<const_iterator, const_iterator>
	equal_range(const _Kt& __k) const
	{
	  auto __res = _Base::equal_range(__k);
	  return { { __res.first, this }, { __res.second, this } };
	}
#endif

      size_type
      erase(const key_type& __key)
      {
	size_type __ret(0);
	size_type __bucket_count = this->bucket_count();
	auto __pair = _Base::equal_range(__key);
	for (auto __victim = __pair.first; __victim != __pair.second;)
	  {
	    _M_invalidate(__victim);
	    __victim = _Base::erase(__victim);
	    ++__ret;
	  }

	_M_check_rehashed(__bucket_count);
	return __ret;
      }

# ifdef __glibcxx_associative_heterogeneous_erasure
      template <__heterogeneous_hash_key<unordered_multimap> _Kt>
	size_type
	erase(_Kt&& __key)
	{
	  size_type __count(0);
	  auto __victims = _Base::equal_range(__key);
	  for (auto __victim = __victims.first; __victim != __victims.second;)
	    {
	      _M_invalidate(__victim);
	      __victim = _Base::erase(__victim);
	      ++__count;
	    }
	  return __count;
	}
#endif

      iterator
      erase(const_iterator __it)
      {
	__glibcxx_check_erase(__it);
	return { _M_erase(__it.base()), this };
      }

      _Base_iterator
      erase(_Base_const_iterator __it)
      {
	__glibcxx_check_erase2(__it);
	return _M_erase(__it);
      }

      iterator
      erase(iterator __it)
      {
	__glibcxx_check_erase(__it);
	return { _M_erase(__it.base()), this };
      }

      iterator
      erase(const_iterator __first, const_iterator __last)
      {
	__glibcxx_check_erase_range(__first, __last);
	for (auto __tmp = __first.base(); __tmp != __last.base(); ++__tmp)
	  {
	    _GLIBCXX_DEBUG_VERIFY(__tmp != _Base::cend(),
				  _M_message(__gnu_debug::__msg_valid_range)
				  ._M_iterator(__first, "first")
				  ._M_iterator(__last, "last"));
	    _M_invalidate(__tmp);
	  }

	size_type __bucket_count = this->bucket_count();
	auto __next = _Base::erase(__first.base(), __last.base());
	_M_check_rehashed(__bucket_count);
	return { __next, this };
      }

      using _Base::rehash;
      using _Base::reserve;

      _Base&
      _M_base() noexcept { return *this; }

      const _Base&
      _M_base() const noexcept { return *this; }

    private:
      void
      _M_check_rehashed(size_type __prev_count)
      {
	if (__prev_count != this->bucket_count())
	  this->_M_invalidate_all();
      }

      void
      _M_invalidate(_Base_const_iterator __victim)
      {
	this->_M_invalidate_if(
	  [__victim](_Base_const_iterator __it) { return __it == __victim; });
	this->_M_invalidate_local_if(
	  [__victim](_Base_const_local_iterator __it)
	  { return __it == __victim; });
      }

      _Base_iterator
      _M_erase(_Base_const_iterator __victim)
      {
	_M_invalidate(__victim);
	size_type __bucket_count = this->bucket_count();
	_Base_iterator __next = _Base::erase(__victim);
	_M_check_rehashed(__bucket_count);
	return __next;
      }

#ifdef __glibcxx_node_extract // >= C++17 && HOSTED
      node_type
      _M_extract(_Base_const_iterator __victim)
      {
	_M_invalidate(__victim);
	return _Base::extract(__victim);
      }
#endif
    };

#if __cpp_deduction_guides >= 201606

  template<typename _InputIterator,
	   typename _Hash = hash<__iter_key_t<_InputIterator>>,
	   typename _Pred = equal_to<__iter_key_t<_InputIterator>>,
	   typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireNotAllocator<_Pred>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator,
		       unordered_multimap<int, int>::size_type = {},
		       _Hash = _Hash(), _Pred = _Pred(),
		       _Allocator = _Allocator())
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>, _Hash, _Pred,
			  _Allocator>;

  template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
	   typename _Pred = equal_to<_Key>,
	   typename _Allocator = allocator<pair<const _Key, _Tp>>,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireNotAllocator<_Pred>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>,
		       unordered_multimap<int, int>::size_type = {},
		       _Hash = _Hash(), _Pred = _Pred(),
		       _Allocator = _Allocator())
    -> unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>;

  template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator,
		       unordered_multimap<int, int>::size_type, _Allocator)
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>,
			  hash<__iter_key_t<_InputIterator>>,
			  equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

  template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator, _Allocator)
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>,
			  hash<__iter_key_t<_InputIterator>>,
			  equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

  template<typename _InputIterator, typename _Hash, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator,
		       unordered_multimap<int, int>::size_type, _Hash,
		       _Allocator)
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>, _Hash,
			  equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

  template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>,
		       unordered_multimap<int, int>::size_type,
		       _Allocator)
    -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

  template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>, _Allocator)
    -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

  template<typename _Key, typename _Tp, typename _Hash, typename _Allocator,
	   typename = _RequireNotAllocatorOrIntegral<_Hash>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>,
		       unordered_multimap<int, int>::size_type,
		       _Hash, _Allocator)
    -> unordered_multimap<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;

#if __glibcxx_containers_ranges // C++ >= 23
  template<ranges::input_range _Rg,
	   __not_allocator_like _Hash = hash<__detail::__range_key_type<_Rg>>,
	   __not_allocator_like _Pred = equal_to<__detail::__range_key_type<_Rg>>,
	   __allocator_like _Allocator =
	     allocator<__detail::__range_to_alloc_type<_Rg>>>
    unordered_multimap(from_range_t, _Rg&&,
		       unordered_multimap<int, int>::size_type = {},
		       _Hash = _Hash(), _Pred = _Pred(),
		       _Allocator = _Allocator())
    -> unordered_multimap<__detail::__range_key_type<_Rg>,
			  __detail::__range_mapped_type<_Rg>,
			  _Hash, _Pred, _Allocator>;

  template<ranges::input_range _Rg,
	   __allocator_like _Allocator>
    unordered_multimap(from_range_t, _Rg&&, unordered_multimap<int, int>::size_type,
		  _Allocator)
    -> unordered_multimap<__detail::__range_key_type<_Rg>,
			  __detail::__range_mapped_type<_Rg>,
			  hash<__detail::__range_key_type<_Rg>>,
			  equal_to<__detail::__range_key_type<_Rg>>,
			  _Allocator>;

  template<ranges::input_range _Rg,
	   __allocator_like _Allocator>
    unordered_multimap(from_range_t, _Rg&&, _Allocator)
    -> unordered_multimap<__detail::__range_key_type<_Rg>,
			  __detail::__range_mapped_type<_Rg>,
			  hash<__detail::__range_key_type<_Rg>>,
			  equal_to<__detail::__range_key_type<_Rg>>,
			  _Allocator>;

  template<ranges::input_range _Rg,
	   __not_allocator_like _Hash,
	   __allocator_like _Allocator>
    unordered_multimap(from_range_t, _Rg&&,
		       unordered_multimap<int, int>::size_type,
		       _Hash, _Allocator)
    -> unordered_multimap<__detail::__range_key_type<_Rg>,
			  __detail::__range_mapped_type<_Rg>,
			  _Hash, equal_to<__detail::__range_key_type<_Rg>>,
			  _Allocator>;
#endif
#endif

  template<typename _Key, typename _Tp, typename _Hash,
	   typename _Pred, typename _Alloc>
    inline void
    swap(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    noexcept(noexcept(__x.swap(__y)))
    { __x.swap(__y); }

  template<typename _Key, typename _Tp, typename _Hash,
	   typename _Pred, typename _Alloc>
    inline bool
    operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return __x._M_base() == __y._M_base(); }

#if __cpp_impl_three_way_comparison < 201907L
  template<typename _Key, typename _Tp, typename _Hash,
	   typename _Pred, typename _Alloc>
    inline bool
    operator!=(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return !(__x == __y); }
#endif

} // namespace __debug

#ifdef __glibcxx_erase_if // C++ >= 20 && HOSTED
_GLIBCXX_BEGIN_NAMESPACE_VERSION
  template<typename _Key, typename _Tp, typename _Hash, typename _CPred,
	   typename _Alloc, typename _Predicate>
    inline typename __debug::unordered_map<_Key, _Tp, _Hash,
					   _CPred, _Alloc>::size_type
    erase_if(__debug::unordered_map<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
	     _Predicate __pred)
    { return __detail::__erase_nodes_if(__cont, __cont._M_base(), __pred); }

  template<typename _Key, typename _Tp, typename _Hash, typename _CPred,
	   typename _Alloc, typename _Predicate>
    inline typename __debug::unordered_multimap<_Key, _Tp, _Hash,
						_CPred, _Alloc>::size_type
    erase_if(__debug::unordered_multimap<_Key, _Tp, _Hash, _CPred, _Alloc>& __cont,
	     _Predicate __pred)
    { return __detail::__erase_nodes_if(__cont, __cont._M_base(), __pred); }
_GLIBCXX_END_NAMESPACE_VERSION
#endif // __glibcxx_erase_if
} // namespace std

#endif // C++11

#endif