[PATCH] libstdc++: Limit allocations in _Rb_tree 1/2

["François Dumont" <frs.dumont@gmail.com>]

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Here is eventually a working proposal.

Compared to the unordered container approach we need to find out what 
type is going to be used to call the comparer. Otherwise we might 
reinstantiate a temporary each time we call the comparer. For example in 
case of const char* insertion with a less<string_view> comparer we would 
create a string_view instance on each comparer call and so each time do 
a strlen.

This code is tricky and do not cover all use cases. For those uncovered 
cases the default behavior is to create a key_type instance which will 
be moved to storage if needed.

Is there any plan to create a builtin function to get help from the 
compiler to find out this type ? Something like std::invoke_result but 
giving also the actual argument types.

     libstdc++: [_Rb_tree] Limit allocations on unique insertions [PR 96088]

     Detect when invoking the comparer requires an allocation using the 
noexcept
     qualification of the functor. In this case guess the type needed to 
invoke
     the comparer and create a temporary instance used for all comparer 
invocations.
     This temporary instance will be eventually moved to storage 
location if it is to
     insert. Avoid to allocate a node and construct the stored value 
otherwise.

     libstdc++-v3/ChangeLog:

             PR libstdc++/96088
             * include/bits/stl_function.h
             (std::less<>::operator()): Add noexcept qualification.
             (std::greater::operator()): Likewise.
(std::_Identity<>::operator<_Tp2>(_Tp2&&)): New perfect forwarding operator.
(std::_Select1st<>::operator<_Pair2>(_Pair2&&)): New move operator.
             * include/bits/stl_tree.h 
(_Rb_tree<>::_ConvertToValueType<>): New helper type.
             (_Rb_tree<>::__has_firstargument): Likewise.
             (_Rb_tree<>::_S_get_key_type_aux): New helper method, use 
latter.
             (_Rb_tree<>::_S_get_key_type): New helper method, use latter.
             (_Rb_tree<>::__key_type_t): New.
             (_Rb_tree<>::__is_comparable_lhs): New.
             (_Rb_tree<>::__is_comparable_rhs): New.
             (_Rb_tree<>::__is_comparable): New, use latters.
             (_Rb_tree<>::__is_nothrow_comparable_lhs): New.
             (_Rb_tree<>::__is_nothrow_comparable_rhs): New.
             (_Rb_tree<>::__is_nothrow_comparable): New, use latters.
             (_Rb_tree<>::_S_forward_key): New.
             (_Rb_tree<>::_M_get_insert_unique_pos_tr): New.
             (_Rb_tree<>::_M_emplace_unique_kv): New.
             (_Rb_tree<>::_M_emplace_unique_aux): New, use latter.
             (_Rb_tree<>::_M_emplace_unique): New, use latter.
             (_Rb_tree<>::_Auto_node::_S_build): New.
             * testsuite/23_containers/map/96088.cc: New test case.
             * testsuite/23_containers/multimap/96088.cc: New test case.
             * testsuite/23_containers/multiset/96088.cc: New test case.
             * testsuite/23_containers/set/96088.cc: New test case.

François

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diff --git a/libstdc++-v3/include/bits/stl_function.h b/libstdc++-v3/include/bits/stl_function.h
index fa03f32b1b8..f8817e2f6ae 100644
--- a/libstdc++-v3/include/bits/stl_function.h
+++ b/libstdc++-v3/include/bits/stl_function.h
@@ -395,6 +395,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _GLIBCXX14_CONSTEXPR
       bool
       operator()(const _Tp& __x, const _Tp& __y) const
+	_GLIBCXX_NOEXCEPT_IF( noexcept(__x > __y) )
       { return __x > __y; }
     };
 
@@ -405,6 +406,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _GLIBCXX14_CONSTEXPR
       bool
       operator()(const _Tp& __x, const _Tp& __y) const
+	_GLIBCXX_NOEXCEPT_IF( noexcept(__x < __y) )
       { return __x < __y; }
     };
 
@@ -1165,6 +1167,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const _Tp&
       operator()(const _Tp& __x) const
       { return __x; }
+
+#if __cplusplus >= 201103L
+    template<typename _Tp2>
+      _Tp2&&
+      operator()(_Tp2&& __x) const noexcept
+      { return std::forward<_Tp2>(__x); }
+#endif
     };
 
   // Partial specialization, avoids confusing errors in e.g. std::set<const T>.
@@ -1183,15 +1192,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       { return __x.first; }
 
 #if __cplusplus >= 201103L
+    private:
       template<typename _Pair2>
-        typename _Pair2::first_type&
-        operator()(_Pair2& __x) const
-        { return __x.first; }
+	struct __1st_type
+	{ using type = typename _Pair2::first_type; };
+
+      template<typename _Tp, typename _Up>
+	struct __1st_type<pair<_Tp, _Up>>
+	{ using type = _Tp; };
 
+      template<typename _Tp, typename _Up>
+	struct __1st_type<const pair<_Tp, _Up>>
+	{ using type = const _Tp; };
+
+      template<typename _Pair2>
+	struct __1st_type<_Pair2&>
+	{ using type = typename __1st_type<_Pair2>::type&; };
+
+    public:
       template<typename _Pair2>
-        const typename _Pair2::first_type&
-        operator()(const _Pair2& __x) const
-        { return __x.first; }
+	typename __1st_type<_Pair2>::type&&
+	operator()(_Pair2&& __x) const noexcept
+	{ return std::forward<_Pair2>(__x).first; }
 #endif
     };
 
diff --git a/libstdc++-v3/include/bits/stl_tree.h b/libstdc++-v3/include/bits/stl_tree.h
index 3c331fbc952..5dae42a504c 100644
--- a/libstdc++-v3/include/bits/stl_tree.h
+++ b/libstdc++-v3/include/bits/stl_tree.h
@@ -534,6 +534,137 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_Rb_tree& _M_t;
       };
 
+#if __cplusplus >= 201103L
+      template<typename _ExKey, typename _Value>
+	struct _ConvertToValueType;
+
+      template<typename _Value>
+	struct _ConvertToValueType<std::_Identity<_Value>, _Value>
+	{
+	  template<typename _Kt>
+	    constexpr _Kt&&
+	    operator()(_Kt&& __k) const noexcept
+	    { return std::forward<_Kt>(__k); }
+	};
+
+      template<typename _Value>
+	struct _ConvertToValueType<std::_Select1st<_Value>, _Value>
+	{
+	  constexpr _Value&&
+	  operator()(_Value&& __x) const noexcept
+	  { return std::move(__x); }
+
+	  constexpr const _Value&
+	  operator()(const _Value& __x) const noexcept
+	  { return __x; }
+
+	  template<typename _Kt, typename _Vt>
+	    constexpr std::pair<_Kt, _Vt>&&
+	    operator()(std::pair<_Kt, _Vt>&& __x) const noexcept
+	    { return std::move(__x); }
+
+	  template<typename _Kt, typename _Vt>
+	    constexpr const std::pair<_Kt, _Vt>&
+	    operator()(const std::pair<_Kt, _Vt>& __x) const noexcept
+	    { return __x; }
+      };
+
+      template<typename _Func, typename _Kt, typename = __void_t<>>
+	struct __has_first_argument
+	{ };
+
+      template<typename _Func, typename _Kt>
+	struct __has_first_argument<_Func, _Kt,
+				__void_t<typename _Func::first_argument_type>>
+	{ using type = typename _Func::first_argument_type; };
+
+      template<typename _Func, typename _Kt>
+	using __has_first_argument_t
+	  = typename __has_first_argument<_Func, _Kt>::type;
+
+      template<typename _Func, typename _Kt,
+	       typename = __has_first_argument_t<_Func, _Kt>>
+	static typename _Func::first_argument_type
+	_S_get_key_type_aux(const _Func&, _Kt&& __kt);
+
+      template<typename _Func, typename _Kt>
+	static _Key
+	_S_get_key_type_aux(...);
+
+#if __cplusplus >= 201402L
+      template<typename _Func, typename _Kt,
+	       typename = __has_is_transparent_t<_Func, _Kt>>
+	static auto
+	_S_get_key_type(const _Func&, _Kt&& __kt)
+	-> decltype(std::forward<_Kt>(__kt));
+#endif
+
+      template<typename _Arg, typename _Kt>
+	static _Arg
+	_S_get_key_type(bool (*)(const _Arg&, const _Arg&), _Kt&&);
+
+      template<typename _Func, typename _Kt>
+	static auto
+	_S_get_key_type(const _Func& __func, _Kt&& __kt)
+	-> decltype(_S_get_key_type_aux(__func, std::forward<_Kt>(__kt)));
+
+      template<typename _Kt>
+	using __key_type_t = decltype(_S_get_key_type(
+		std::declval<_Compare>(), std::declval<_Kt>()));
+
+      template<typename _Kt>
+	using __is_comparable_lhs =
+	  __is_invocable<_Compare&, _Kt, const _Key&>;
+
+      template<typename _Kt>
+	using __is_comparable_rhs =
+	  __is_invocable<_Compare&, const _Key&, _Kt>;
+
+      template<typename _Kt>
+	using __is_comparable =
+	  __and_<__is_comparable_lhs<_Kt>, __is_comparable_rhs<_Kt>>;
+
+      template<typename _Kt>
+	using __is_nothrow_comparable_lhs =
+	  __is_nothrow_invocable<_Compare&, _Kt, const _Key&>;
+
+      template<typename _Kt>
+	using __is_nothrow_comparable_rhs =
+	  __is_nothrow_invocable<_Compare&, const _Key&, _Kt>;
+
+      template<typename _Kt>
+	using __is_nothrow_comparable =
+	  __and_<__is_nothrow_comparable_lhs<_Kt>,
+		 __is_nothrow_comparable_rhs<_Kt>>;
+
+      template<typename _Kt>
+	static __enable_if_t<
+	  __and_<__not_<is_same<__key_type_t<_Kt>, _Key>>,
+		 __is_comparable<__key_type_t<_Kt>>>::value,
+	  __conditional_t<
+	    __and_<__is_nothrow_comparable_lhs<const _Key&>,
+		   __not_<__is_nothrow_comparable<__key_type_t<_Kt>>>>::value,
+	    _Key, __key_type_t<_Kt>>>
+	_S_forward_key(_Kt&& __k)
+	{ return std::forward<_Kt>(__k); }
+
+      template<typename _Kt>
+	static __enable_if_t<
+	  __or_<is_same<__key_type_t<_Kt>, _Key>,
+		__not_<__is_comparable<__key_type_t<_Kt>>>>::value,
+	  _Key>
+	_S_forward_key(_Kt&& __k)
+	{ return { std::forward<_Kt>(__k) }; }
+
+      static const _Key&
+      _S_forward_key(const _Key& __k)
+      { return __k; }
+
+      static _Key&&
+      _S_forward_key(_Key&& __k)
+      { return std::move(__k); }
+#endif // C++11
+
     public:
       typedef _Key 				key_type;
       typedef _Val 				value_type;
@@ -833,6 +964,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       pair<_Base_ptr, _Base_ptr>
       _M_get_insert_equal_pos(const key_type& __k);
 
+#if __cplusplus >= 201103L
+      template<typename _Kt>
+	pair<_Base_ptr, _Base_ptr>
+	_M_get_insert_unique_pos_tr(const _Kt& __k);
+#endif
+
       pair<_Base_ptr, _Base_ptr>
       _M_get_insert_hint_unique_pos(const_iterator __pos,
 				    const key_type& __k);
@@ -1075,6 +1212,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  return _M_insert_equal_(__pos, std::forward<_Arg>(__x), __an);
 	}
 
+      template<typename _Kt, typename _Arg>
+	std::pair<iterator, bool>
+	_M_emplace_unique_kv(_Kt&&, _Arg&&);
+
+      template<typename _Arg>
+	pair<iterator, bool>
+	_M_emplace_unique_aux(_Arg&& __arg)
+	{
+	  return _M_emplace_unique_kv(
+	    _S_forward_key(_KeyOfValue{}(std::forward<_Arg>(__arg))),
+	    std::forward<_Arg>(__arg));
+	}
+
+      template<typename _Arg>
+	pair<iterator, bool>
+	_M_emplace_unique(_Arg&& __arg)
+	{
+	  using __to_value = _ConvertToValueType<_KeyOfValue, value_type>;
+	  return _M_emplace_unique_aux(__to_value{}(std::forward<_Arg>(__arg)));
+	}
+
       template<typename... _Args>
 	pair<iterator, bool>
 	_M_emplace_unique(_Args&&... __args);
@@ -1667,6 +1825,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  return __it;
 	}
 
+	template<typename _Kt, typename _Arg, typename _Value>
+	  static _Auto_node
+	  _S_build(_Rb_tree& __t,
+		   _Kt&& __k, _Arg&& __arg, std::_Select1st<_Value>)
+	  {
+	    return
+	      { __t, std::forward<_Kt>(__k), std::forward<_Arg>(__arg).second };
+	  }
+
+	template<typename _Kt, typename _Arg, typename _Value>
+	  static _Auto_node
+	  _S_build(_Rb_tree& __t, _Kt&& __k, _Arg&&, std::_Identity<_Value>)
+	  { return { __t, std::forward<_Kt>(__k) }; }
+
 	_Rb_tree& _M_t;
 	_Link_type _M_node;
       };
@@ -2152,6 +2324,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       return _Res(__x, __y);
     }
 
+#if __cplusplus >= 201103L
+  template<typename _Key, typename _Val, typename _KeyOfValue,
+	   typename _Compare, typename _Alloc>
+    template<typename _Kt>
+      auto
+      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
+      _M_get_insert_unique_pos_tr(const _Kt& __k)
+      -> pair<_Base_ptr, _Base_ptr>
+      {
+	typedef pair<_Base_ptr, _Base_ptr> _Res;
+	_Link_type __x = _M_begin();
+	_Base_ptr __y = _M_end();
+	bool __comp = true;
+	while (__x != 0)
+	  {
+	    __y = __x;
+	    __comp = _M_impl._M_key_compare(__k, _S_key(__x));
+	    __x = __comp ? _S_left(__x) : _S_right(__x);
+	  }
+	iterator __j = iterator(__y);
+	if (__comp)
+	  {
+	    if (__j == begin())
+	      return _Res(__x, __y);
+	    else
+	      --__j;
+	  }
+	if (_M_impl._M_key_compare(_S_key(__j._M_node), __k))
+	  return _Res(__x, __y);
+	return _Res(__j._M_node, 0);
+      }
+#endif
+
   template<typename _Key, typename _Val, typename _KeyOfValue,
 	   typename _Compare, typename _Alloc>
 #if __cplusplus >= 201103L
@@ -2438,6 +2643,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return {iterator(__res.first), false};
       }
 
+  template<typename _Key, typename _Val, typename _KeyOfValue,
+	   typename _Compare, typename _Alloc>
+    template<typename _Kt, typename _Arg>
+      auto
+      _Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::
+      _M_emplace_unique_kv(_Kt&& __k, _Arg&& __arg)
+      -> pair<iterator, bool>
+      {
+	auto __res = _M_get_insert_unique_pos_tr(__k);
+	if (__res.second)
+	  {
+	    _Auto_node __z = _Auto_node::_S_build(*this,
+	      std::forward<_Kt>(__k), std::forward<_Arg>(__arg), _KeyOfValue{});
+	    return { __z._M_insert(__res), true };
+	  }
+	return { iterator(__res.first), false };
+      }
+
   template<typename _Key, typename _Val, typename _KeyOfValue,
 	   typename _Compare, typename _Alloc>
     template<typename... _Args>
diff --git a/libstdc++-v3/testsuite/23_containers/map/96088.cc b/libstdc++-v3/testsuite/23_containers/map/96088.cc
new file mode 100644
index 00000000000..17c809240f4
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/map/96088.cc
@@ -0,0 +1,325 @@
+// { dg-do run { target c++17 } }
+// { dg-require-effective-target std_allocator_new }
+
+// Copyright (C) 2023 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// libstdc++/96088
+
+#include <string_view>
+#include <string>
+#include <map>
+#include <vector>
+
+#include <testsuite_hooks.h>
+#include <replacement_memory_operators.h>
+
+static constexpr std::initializer_list<std::pair<const char*, int>> lst =
+  { {"long_str_for_dynamic_allocating", 1} };
+
+void
+test01()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+
+  VERIFY( !m.emplace(*lst.begin()).second );
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 4 );
+}
+
+void
+test02()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int, std::less<std::string_view>> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  VERIFY( !m.emplace(*lst.begin()).second );
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+bool
+less_string_f(const std::string& lhs, const std::string& rhs) noexcept
+{ return lhs < rhs; }
+
+void
+test11()
+{
+  typedef bool (*less_string_t)(const std::string&,
+				const std::string&) noexcept;
+  __gnu_test::counter::reset();
+  less_string_t comparer = &less_string_f;
+  std::map<std::string, int, less_string_t> m(comparer);
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+bool
+less_string_view_f(const std::string_view& lhs,
+		   const std::string_view& rhs) noexcept
+{ return lhs < rhs; }
+
+void
+test12()
+{
+  typedef bool (*less_stringview_t) (const std::string_view&,
+				     const std::string_view&) noexcept;
+  __gnu_test::counter::reset();
+  less_stringview_t comparer = &less_string_view_f;
+  std::map<std::string, int, less_stringview_t> m(comparer);
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+struct less_string_functor
+{
+  bool
+  operator()(const std::string& lhs,
+	     const std::string& rhs) const noexcept
+  { return lhs < rhs; }
+};
+
+void
+test21()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int, less_string_functor> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+struct less_string_view_noexcept_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const noexcept
+  { return lhs < rhs; }
+};
+
+void
+test22()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int, less_string_view_noexcept_functor> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+struct less_string_view_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const
+  { return lhs < rhs; }
+};
+
+void
+test23()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int, less_string_view_functor> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+struct less_string_view_noexcept_transparent_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const noexcept
+  { return lhs < rhs; }
+
+  typedef std::__is_transparent is_transparent;
+};
+
+void
+test24()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int,
+	   less_string_view_noexcept_transparent_functor> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+struct less_string_view_transparent_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const
+  { return lhs < rhs; }
+
+  typedef std::__is_transparent is_transparent;
+};
+
+void
+test25()
+{
+  __gnu_test::counter::reset();
+  std::map<std::string, int, less_string_view_transparent_functor> m;
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  m.insert(lst.begin(), lst.end());
+  VERIFY( m.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+void
+test03()
+{
+  std::vector<std::pair<std::string, int>> v;
+  v.insert(v.end(), lst.begin(), lst.end());
+
+  const auto origin = __gnu_test::counter::count();
+
+  {
+    __gnu_test::counter::reset();
+    std::map<std::string, int, std::less<std::string_view>> m;
+    m.insert(v.begin(), v.end());
+    VERIFY( m.size() == 1 );
+
+    // Allocate a node and the std::string (unless COW).
+    constexpr std::size_t increments = _GLIBCXX_USE_CXX11_ABI ? 2 : 1;
+
+    VERIFY( __gnu_test::counter::count() == origin + increments );
+    VERIFY( __gnu_test::counter::get()._M_increments == increments );
+
+    m.insert(v.begin(), v.end());
+    VERIFY( m.size() == 1 );
+
+    VERIFY( __gnu_test::counter::count() == origin + increments );
+    VERIFY( __gnu_test::counter::get()._M_increments == increments );
+  }
+  VERIFY( __gnu_test::counter::count() == origin );
+
+  {
+    __gnu_test::counter::reset();
+    std::map<std::string, int, std::less<std::string_view>> m;
+    m.insert(std::make_move_iterator(v.begin()),
+	     std::make_move_iterator(v.end()));
+    VERIFY( m.size() == 1 );
+
+    // Allocate a node. String is moved.
+    constexpr std::size_t increments = 1;
+
+    VERIFY( __gnu_test::counter::count() == origin + increments );
+    VERIFY( __gnu_test::counter::get()._M_increments == increments );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test11();
+  test12();
+  test21();
+  test22();
+  test23();
+  test24();
+  test25();
+  test03();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/multimap/96088.cc b/libstdc++-v3/testsuite/23_containers/multimap/96088.cc
new file mode 100644
index 00000000000..919c5e59c71
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/multimap/96088.cc
@@ -0,0 +1,65 @@
+// { dg-do run { target c++17 } }
+// { dg-require-effective-target std_allocator_new }
+
+// Copyright (C) 2023 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// libstdc++/96088
+
+#include <string_view>
+#include <string>
+#include <map>
+
+#include <testsuite_hooks.h>
+#include <replacement_memory_operators.h>
+
+static constexpr std::initializer_list<std::pair<const char*, int>> lst = {
+    {"long_str_for_dynamic_allocating", 1}
+};
+
+void
+test01()
+{
+  __gnu_test::counter::reset();
+  std::multimap<std::string, int,
+		std::less<std::string_view>> foo;
+  foo.insert(lst.begin(), lst.end());
+  VERIFY( foo.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+void
+test02()
+{
+  __gnu_test::counter::reset();
+  std::multimap<std::string, int> foo;
+  foo.insert(lst.begin(), lst.end());
+  VERIFY( foo.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/multiset/96088.cc b/libstdc++-v3/testsuite/23_containers/multiset/96088.cc
new file mode 100644
index 00000000000..2cdc08aba51
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/multiset/96088.cc
@@ -0,0 +1,64 @@
+// { dg-do run { target c++17 } }
+// { dg-require-effective-target std_allocator_new }
+
+// Copyright (C) 2023 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// libstdc++/96088
+
+#include <string_view>
+#include <string>
+#include <set>
+
+#include <testsuite_hooks.h>
+#include <replacement_memory_operators.h>
+
+static constexpr std::initializer_list<const char*> lst = {
+  "long_str_for_dynamic_allocating"
+};
+
+void
+test01()
+{
+  __gnu_test::counter::reset();
+  std::multiset<std::string, std::less<std::string_view>> foo;
+  foo.insert(lst.begin(), lst.end());
+  VERIFY( foo.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+void
+test02()
+{
+  __gnu_test::counter::reset();
+  std::multiset<std::string> foo;
+  foo.insert(lst.begin(), lst.end());
+  VERIFY( foo.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/23_containers/set/96088.cc b/libstdc++-v3/testsuite/23_containers/set/96088.cc
new file mode 100644
index 00000000000..a6da8ecda27
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/set/96088.cc
@@ -0,0 +1,325 @@
+// { dg-do run { target c++17 } }
+// { dg-require-effective-target std_allocator_new }
+
+// Copyright (C) 2023 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// libstdc++/96088
+
+#include <string_view>
+#include <string>
+#include <set>
+#include <vector>
+
+#include <testsuite_hooks.h>
+#include <replacement_memory_operators.h>
+
+static constexpr std::initializer_list<const char*> lst = {
+  "long_str_for_dynamic_allocating"
+};
+
+void
+test01()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string, std::greater<std::string>> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+
+  s.emplace(*lst.begin());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 4 );
+}
+
+void
+test02()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string, std::greater<std::string_view>> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.emplace(*lst.begin());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+bool
+less_string_f(const std::string& lhs, const std::string& rhs) noexcept
+{ return lhs < rhs; }
+
+void
+test11()
+{
+  typedef bool (*less_string_t)(const std::string&,
+				const std::string&) noexcept;
+  __gnu_test::counter::reset();
+  less_string_t less = &less_string_f;
+  std::set<std::string, less_string_t> s(less);
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+bool
+less_string_view_f(const std::string_view& lhs,
+		   const std::string_view& rhs) noexcept
+{ return lhs < rhs; }
+
+void
+test12()
+{
+  typedef bool (*less_stringview_t)(const std::string_view&,
+				    const std::string_view&) noexcept;
+  __gnu_test::counter::reset();
+  less_stringview_t less = &less_string_view_f;
+  std::set<std::string, less_stringview_t> s(less);
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+struct less_string_functor
+{
+  bool
+  operator()(const std::string& lhs, const std::string& rhs) const noexcept
+  { return lhs < rhs; }
+};
+
+void
+test21()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string, less_string_functor> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+struct less_string_view_noexcept_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const noexcept
+  { return lhs < rhs; }
+};
+
+void
+test22()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string, less_string_view_noexcept_functor> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+struct less_string_view_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const
+  { return lhs < rhs; }
+};
+
+void
+test23()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string, less_string_view_functor> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 3 );
+}
+
+struct less_string_view_noexcept_transparent_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const noexcept
+  { return lhs < rhs; }
+
+  typedef std::__is_transparent is_transparent;
+};
+
+void
+test24()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string,
+	   less_string_view_noexcept_transparent_functor> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+struct less_string_view_transparent_functor
+{
+  bool
+  operator()(const std::string_view& lhs,
+	     const std::string_view& rhs) const
+  { return lhs < rhs; }
+
+  typedef std::__is_transparent is_transparent;
+};
+
+void
+test25()
+{
+  __gnu_test::counter::reset();
+  std::set<std::string, less_string_view_transparent_functor> s;
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+
+  s.insert(lst.begin(), lst.end());
+  VERIFY( s.size() == 1 );
+
+  VERIFY( __gnu_test::counter::count() == 2 );
+  VERIFY( __gnu_test::counter::get()._M_increments == 2 );
+}
+
+void
+test03()
+{
+  std::vector<std::string> v;
+  v.insert(v.end(), lst.begin(), lst.end());
+
+  const auto origin = __gnu_test::counter::count();
+
+  {
+    __gnu_test::counter::reset();
+    std::set<std::string, std::less<std::string_view>> s;
+    s.insert(v.begin(), v.end());
+    VERIFY( s.size() == 1 );
+
+    // Allocate a node and the std::string (unless COW).
+    constexpr std::size_t increments = _GLIBCXX_USE_CXX11_ABI ? 2 : 1;
+
+    VERIFY( __gnu_test::counter::count() == origin + increments );
+    VERIFY( __gnu_test::counter::get()._M_increments == increments );
+
+    s.insert(v.begin(), v.end());
+    VERIFY( s.size() == 1 );
+
+    VERIFY( __gnu_test::counter::count() == origin + increments );
+    VERIFY( __gnu_test::counter::get()._M_increments == increments );
+  }
+  VERIFY( __gnu_test::counter::count() == origin );
+
+  {
+    __gnu_test::counter::reset();
+    std::set<std::string, std::less<std::string_view>> s;
+    s.insert(std::make_move_iterator(v.begin()),
+	     std::make_move_iterator(v.end()));
+    VERIFY( s.size() == 1 );
+
+    // Allocate a node, string is moved.
+    constexpr std::size_t increments = 1;
+
+    VERIFY( __gnu_test::counter::count() == origin + increments );
+    VERIFY( __gnu_test::counter::get()._M_increments == increments );
+  }
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test11();
+  test12();
+  test21();
+  test22();
+  test23();
+  test24();
+  test25();
+  test03();
+  return 0;
+}