Index: uspace/lib/cpp/include/impl/set.hpp
===================================================================
--- uspace/lib/cpp/include/impl/set.hpp	(revision 89bc64601cfdf838fc123ada605c9bae3dd2acbe)
+++ uspace/lib/cpp/include/impl/set.hpp	(revision 7644d6e186ece59bb16ff427b3b0e2fcea5c7d3b)
@@ -522,3 +522,472 @@
         return false;
     }
+    /**
+     * 23.4.7, class template multiset:
+     */
+
+    template<
+        class Key,
+        class Compare = less<Key>,
+        class Alloc = allocator<Key>
+    >
+    class multiset
+    {
+        public:
+            using key_type        = Key;
+            using value_type      = Key;
+            using key_compare     = Compare;
+            using value_compare   = Compare;
+            using allocator_type  = Alloc;
+            using pointer         = typename allocator_traits<allocator_type>::pointer;
+            using const_pointer   = typename allocator_traits<allocator_type>::const_pointer;
+            using reference       = value_type&;
+            using const_reference = const value_type&;
+            using size_type       = size_t;
+            using difference_type = ptrdiff_t;
+
+            /**
+             * Note: Both the iterator and const_iterator (and their local variants)
+             *       types are constant iterators, the standard does not require them
+             *       to be the same type, but why not? :)
+             */
+            using iterator             = aux::rbtree_const_iterator<
+                value_type, const_reference, const_pointer, size_type
+            >;
+            using const_iterator       = iterator;
+
+            using reverse_iterator       = std::reverse_iterator<iterator>;
+            using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+
+            multiset()
+                : multiset{key_compare{}}
+            { /* DUMMY BODY */ }
+
+            explicit multiset(const key_compare& comp,
+                              const allocator_type& alloc = allocator_type{})
+                : tree_{comp}, allocator_{alloc}
+            { /* DUMMY BODY */ }
+
+            template<class InputIterator>
+            multiset(InputIterator first, InputIterator last,
+                     const key_compare& comp = key_compare{},
+                     const allocator_type& alloc = allocator_type{})
+                : multiset{comp, alloc}
+            {
+                insert(first, last);
+            }
+
+            multiset(const multiset& other)
+                : multiset{other, other.allocator_}
+            { /* DUMMY BODY */ }
+
+            multiset(multiset&& other)
+                : tree_{move(other.tree_)}, allocator_{move(other.allocator_)}
+            { /* DUMMY BODY */ }
+
+            explicit multiset(const allocator_type& alloc)
+                : tree_{}, allocator_{alloc}
+            { /* DUMMY BODY */ }
+
+            multiset(const multiset& other, const allocator_type& alloc)
+                : tree_{other.tree_}, allocator_{alloc}
+            { /* DUMMY BODY */ }
+
+            multiset(multiset&& other, const allocator_type& alloc)
+                : tree_{move(other.tree_)}, allocator_{alloc}
+            { /* DUMMY BODY */ }
+
+            multiset(initializer_list<value_type> init,
+                     const key_compare& comp = key_compare{},
+                     const allocator_type& alloc = allocator_type{})
+                : multiset{comp, alloc}
+            {
+                insert(init.begin(), init.end());
+            }
+
+            template<class InputIterator>
+            multiset(InputIterator first, InputIterator last,
+                     const allocator_type& alloc)
+                : multiset{first, last, key_compare{}, alloc}
+            { /* DUMMY BODY */ }
+
+            multiset(initializer_list<value_type> init,
+                     const allocator_type& alloc)
+                : multiset{init, key_compare{}, alloc}
+            { /* DUMMY BODY */ }
+
+            ~multiset()
+            { /* DUMMY BODY */ }
+
+            multiset& operator=(const multiset& other)
+            {
+                tree_ = other.tree_;
+                allocator_ = other.allocator_;
+
+                return *this;
+            }
+
+            multiset& operator=(multiset&& other)
+                noexcept(allocator_traits<allocator_type>::is_always_equal::value &&
+                         is_nothrow_move_assignable<key_compare>::value)
+            {
+                tree_ = move(other.tree_);
+                allocator_ = move(other.allocator_);
+
+                return *this;
+            }
+
+            multiset& operator=(initializer_list<value_type>& init)
+            {
+                tree_.clear();
+
+                insert(init.begin(), init.end());
+
+                return *this;
+            }
+
+            allocator_type get_allocator() const noexcept
+            {
+                return allocator_;
+            }
+
+            iterator begin() noexcept
+            {
+                return tree_.begin();
+            }
+
+            const_iterator begin() const noexcept
+            {
+                return tree_.begin();
+            }
+
+            iterator end() noexcept
+            {
+                return tree_.end();
+            }
+
+            const_iterator end() const noexcept
+            {
+                return tree_.end();
+            }
+
+            reverse_iterator rbegin() noexcept
+            {
+                return tree_.rbegin();
+            }
+
+            const_reverse_iterator rbegin() const noexcept
+            {
+                return tree_.rbegin();
+            }
+
+            reverse_iterator rend() noexcept
+            {
+                return tree_.rend();
+            }
+
+            const_reverse_iterator rend() const noexcept
+            {
+                return tree_.rend();
+            }
+
+            const_iterator cbegin() const noexcept
+            {
+                return tree_.cbegin();
+            }
+
+            const_iterator cend() const noexcept
+            {
+                return tree_.cend();
+            }
+
+            const_reverse_iterator crbegin() const noexcept
+            {
+                return tree_.crbegin();
+            }
+
+            const_reverse_iterator crend() const noexcept
+            {
+                return tree_.crend();
+            }
+
+            bool empty() const noexcept
+            {
+                return tree_.empty();
+            }
+
+            size_type size() const noexcept
+            {
+                return tree_.size();
+            }
+
+            size_type max_size() const noexcept
+            {
+                return tree_.max_size(allocator_);
+            }
+
+            template<class... Args>
+            iterator emplace(Args&&... args)
+            {
+                return tree_.emplace(forward<Args>(args)...);
+            }
+
+            template<class... Args>
+            iterator emplace_hint(const_iterator, Args&&... args)
+            {
+                return emplace(forward<Args>(args)...);
+            }
+
+            iterator insert(const value_type& val)
+            {
+                return tree_.insert(val);
+            }
+
+            iterator insert(value_type&& val)
+            {
+                return tree_.insert(forward<value_type>(val));
+            }
+
+            iterator insert(const_iterator, const value_type& val)
+            {
+                return insert(val);
+            }
+
+            iterator insert(const_iterator, value_type&& val)
+            {
+                return insert(forward<value_type>(val));
+            }
+
+            template<class InputIterator>
+            void insert(InputIterator first, InputIterator last)
+            {
+                while (first != last)
+                    insert(*first++);
+            }
+
+            void insert(initializer_list<value_type> init)
+            {
+                insert(init.begin(), init.end());
+            }
+
+            iterator erase(const_iterator position)
+            {
+                return tree_.erase(position);
+            }
+
+            size_type erase(const key_type& key)
+            {
+                return tree_.erase(key);
+            }
+
+            iterator erase(const_iterator first, const_iterator last)
+            {
+                while (first != last)
+                    first = erase(first);
+
+                return iterator{
+                    first.node(), first.end()
+                };
+            }
+
+            void swap(multiset& other)
+                noexcept(allocator_traits<allocator_type>::is_always_equal::value &&
+                         noexcept(std::swap(declval<key_compare>(), declval<key_compare>())))
+            {
+                tree_.swap(other.tree_);
+                std::swap(allocator_, other.allocator_);
+            }
+
+            void clear() noexcept
+            {
+                tree_.clear();
+            }
+
+            key_compare key_comp() const
+            {
+                return tree_.key_comp();
+            }
+
+            value_compare value_comp() const
+            {
+                return tree_.value_comp();
+            }
+
+            iterator find(const key_type& key)
+            {
+                return tree_.find(key);
+            }
+
+            const_iterator find(const key_type& key) const
+            {
+                return tree_.find(key);
+            }
+
+            template<class K>
+            iterator find(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            )
+            {
+                return tree_.find(key);
+            }
+
+            template<class K>
+            const_iterator find(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            ) const
+            {
+                return tree_.find(key);
+            }
+
+            size_type count(const key_type& key) const
+            {
+                return tree_.count(key);
+            }
+
+            template<class K>
+            size_type count(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            ) const
+            {
+                return tree_.count(key);
+            }
+
+            iterator lower_bound(const key_type& key)
+            {
+                return tree_.lower_bound(key);
+            }
+
+            const_iterator lower_bound(const key_type& key) const
+            {
+                return tree_.lower_bound(key);
+            }
+
+            template<class K>
+            iterator lower_bound(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            )
+            {
+                return tree_.lower_bound(key);
+            }
+
+            template<class K>
+            const_iterator lower_bound(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            ) const
+            {
+                return tree_.lower_bound(key);
+            }
+
+            iterator upper_bound(const key_type& key)
+            {
+                return tree_.upper_bound(key);
+            }
+
+            const_iterator upper_bound(const key_type& key) const
+            {
+                return tree_.upper_bound(key);
+            }
+
+            template<class K>
+            iterator upper_bound(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            )
+            {
+                return tree_.upper_bound(key);
+            }
+
+            template<class K>
+            const_iterator upper_bound(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            ) const
+            {
+                return tree_.upper_bound(key);
+            }
+
+            pair<iterator, iterator> equal_range(const key_type& key)
+            {
+                return tree_.equal_range(key);
+            }
+
+            pair<const_iterator, const_iterator> equal_range(const key_type& key) const
+            {
+                return tree_.equal_range(key);
+            }
+
+            template<class K>
+            pair<iterator, iterator> equal_range(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            )
+            {
+                return tree_.equal_range(key);
+            }
+
+            template<class K>
+            pair<const_iterator, const_iterator> equal_range(
+                enable_if_t<aux::is_transparent_v<key_compare>, const K&> key
+            ) const
+            {
+                return tree_.equal_range(key);
+            }
+
+        private:
+            using tree_type = aux::rbtree<
+                key_type, key_type, aux::key_no_value_key_extractor<key_type>,
+                key_compare, allocator_type, size_type,
+                iterator, const_iterator,
+                aux::rbtree_multi_policy
+            >;
+
+            tree_type tree_;
+            allocator_type allocator_;
+
+            template<class K, class C, class A>
+            friend bool operator==(const multiset<K, C, A>&,
+                                   const multiset<K, C, A>&);
+    };
+
+    template<class Key, class Compare, class Allocator>
+    bool operator==(const multiset<Key, Compare, Allocator>& lhs,
+                    const multiset<Key, Compare, Allocator>& rhs)
+    {
+        return lhs.tree_.is_eq_to(rhs.tree_);
+    }
+
+    template<class Key, class Compare, class Allocator>
+    bool operator<(const multiset<Key, Compare, Allocator>& lhs,
+                   const multiset<Key, Compare, Allocator>& rhs)
+    {
+        // TODO: need lexicographical_compare
+        return false;
+    }
+
+    template<class Key, class Compare, class Allocator>
+    bool operator!=(const multiset<Key, Compare, Allocator>& lhs,
+                    const multiset<Key, Compare, Allocator>& rhs)
+    {
+        return !(lhs == rhs);
+    }
+
+    template<class Key, class Compare, class Allocator>
+    bool operator>(const multiset<Key, Compare, Allocator>& lhs,
+                   const multiset<Key, Compare, Allocator>& rhs)
+    {
+        // TODO: need lexicographical_compare
+        return false;
+    }
+
+    template<class Key, class Compare, class Allocator>
+    bool operator>=(const multiset<Key, Compare, Allocator>& lhs,
+                    const multiset<Key, Compare, Allocator>& rhs)
+    {
+        // TODO: need lexicographical_compare
+        return false;
+    }
+
+    template<class Key, class Compare, class Allocator>
+    bool operator<=(const multiset<Key, Compare, Allocator>& lhs,
+                    const multiset<Key, Compare, Allocator>& rhs)
+    {
+        // TODO: need lexicographical_compare
+        return false;
+    }
 }
