Index: uspace/lib/cpp/include/internal/memory/owner_less.hpp
===================================================================
--- uspace/lib/cpp/include/internal/memory/owner_less.hpp	(revision 6a3a64f9ca5ecfac019f3def74bb32509be36d1b)
+++ uspace/lib/cpp/include/internal/memory/owner_less.hpp	(revision 6a3a64f9ca5ecfac019f3def74bb32509be36d1b)
@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2018 Jaroslav Jindrak
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * - The name of the author may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef LIBCPP_INTERNAL_MEMORY_OWNER_LESS
+#define LIBCPP_INTERNAL_MEMORY_OWNER_LESS
+
+#include <internal/memory/shared_ptr.hpp>
+#include <internal/memory/weak_ptr.hpp>
+
+namespace std
+{
+    /**
+     * 20.8.2.4, class template owner_less:
+     */
+
+    template<class>
+    struct owner_less;
+
+    template<class T>
+    struct owner_less<shared_ptr<T>>
+    {
+        using retult_type          = bool;
+        using first_argument_type  = shared_ptr<T>;
+        using second_argument_type = shared_ptr<T>;
+
+        bool operator()(const shared_ptr<T>& lhs, const shared_ptr<T>& rhs) const
+        {
+            return lhs.owner_before(rhs);
+        }
+
+        bool operator()(const shared_ptr<T>& lhs, const weak_ptr<T>& rhs) const
+        {
+            return lhs.owner_before(rhs);
+        }
+
+        bool operator()(const weak_ptr<T>& lhs, const shared_ptr<T>& rhs) const
+        {
+            return lhs.owner_before(rhs);
+        }
+    };
+
+    template<class T>
+    struct owner_less<weak_ptr<T>>
+    {
+        using retult_type          = bool;
+        using first_argument_type  = weak_ptr<T>;
+        using second_argument_type = weak_ptr<T>;
+
+        bool operator()(const weak_ptr<T>& lhs, const weak_ptr<T>& rhs) const
+        {
+            return lhs.owner_before(rhs);
+        }
+
+        bool operator()(const shared_ptr<T>& lhs, const weak_ptr<T>& rhs) const
+        {
+            return lhs.owner_before(rhs);
+        }
+
+        bool operator()(const weak_ptr<T>& lhs, const shared_ptr<T>& rhs) const
+        {
+            return lhs.owner_before(rhs);
+        }
+    };
+}
+
+#endif
Index: uspace/lib/cpp/include/memory
===================================================================
--- uspace/lib/cpp/include/memory	(revision de00da5a3ca2f1d462111955da782499cdba9ade)
+++ uspace/lib/cpp/include/memory	(revision 6a3a64f9ca5ecfac019f3def74bb32509be36d1b)
@@ -30,4 +30,5 @@
 #include <internal/memory/allocator_arg.hpp>
 #include <internal/memory/addressof.hpp>
+#include <internal/memory/owner_less.hpp>
 #include <internal/memory/shared_ptr.hpp>
 #include <internal/memory/weak_ptr.hpp>