--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libstdc++-v3/testsuite/20_util/integer_comparisons/less.cc	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,78 @@
+// Copyright (C) 2020 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/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <utility>
+#include <limits>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  unsigned int u = std::numeric_limits<unsigned int>::max();
+  int s = -1;
+  VERIFY( std::cmp_less(s, u) );
+  VERIFY( !std::cmp_less(u, s) );
+  u = (unsigned) std::numeric_limits<int>::max() + 1U;
+  VERIFY( std::cmp_less(s, u) );
+  VERIFY( !std::cmp_less(u, s) );
+}
+
+constexpr bool
+test02()
+{
+  unsigned int u = std::numeric_limits<unsigned int>::max();
+  int s = -1;
+  if (!std::cmp_less(s, u))
+    throw 1;
+  if (std::cmp_less(u, s))
+    throw 2;
+  return true;
+}
+
+void
+test03()
+{
+  short ss = -1;
+  int s = -1;
+  VERIFY( !std::cmp_less(s, ss) );
+  VERIFY( !std::cmp_less(ss, s) );
+
+  unsigned int u = (unsigned int) -1;
+  VERIFY( std::cmp_less(s, u) );
+  VERIFY( !std::cmp_less(u, s) );
+  VERIFY( std::cmp_less(ss, u) );
+  VERIFY( !std::cmp_less(u, ss) );
+
+  unsigned long long ul = (unsigned long long) -1;
+  VERIFY( std::cmp_less(s, ul) );
+  VERIFY( !std::cmp_less(ul, s) );
+  VERIFY( std::cmp_less(ss, ul) );
+  VERIFY( !std::cmp_less(ul, ss) );
+  VERIFY( std::cmp_less(u, ul) );
+  VERIFY( !std::cmp_less(ul, u) );
+}
+
+int
+main()
+{
+  test01();
+  static_assert( test02() );
+  test03();
+}