libsupc++: Implement comparison algorithms for C++20

This is incomplete because std::strong_order doesn't support
floating-point types.

The partial_order and weak_order tests use VERIFY instead of
static_assert because of PR 92431.

	* libsupc++/compare (strong_order, weak_order, partial_order)
	(compare_strong_order_fallback, compare_weak_order_fallback)
	(compare_partial_order_fallback): Define customization point objects
	for C++20.
	* testsuite/18_support/comparisons/algorithms/partial_order.cc: New
	test.
	* testsuite/18_support/comparisons/algorithms/strong_order.cc: New
	test.
	* testsuite/18_support/comparisons/algorithms/weak_order.cc: New test.

From-SVN: r278149

libstdc++-v3/ChangeLog

+2019-11-13  Jonathan Wakely  <jwakely@redhat.com>
+
+	* libsupc++/compare (strong_order, weak_order, partial_order)
+	(compare_strong_order_fallback, compare_weak_order_fallback)
+	(compare_partial_order_fallback): Define customization point objects
+	for C++20.
+	* testsuite/18_support/comparisons/algorithms/partial_order.cc: New
+	test.
+	* testsuite/18_support/comparisons/algorithms/strong_order.cc: New
+	test.
+	* testsuite/18_support/comparisons/algorithms/weak_order.cc: New test.
+
 2019-11-11  Gerald Pfeifer  <gerald@pfeifer.com>
 
 	* doc/xml/gnu/gpl-3.0.xml: Adjust link to "Why not LGPL".

libstdc++-v3/testsuite/18_support/comparisons/algorithms/partial_order.cc

+// Copyright (C) 2019 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 <compare>
+#include <limits>
+#include <testsuite_hooks.h>
+
+using std::partial_order;
+using std::partial_ordering;
+
+void
+test01()
+{
+  int one = 1, two = 2;
+
+  VERIFY( partial_order(one, two) == partial_ordering::less );
+  VERIFY( partial_order(one, one) == partial_ordering::equivalent );
+  VERIFY( partial_order(two, one) == partial_ordering::greater );
+  static_assert( noexcept(partial_order(1, 1)) );
+}
+
+constexpr partial_ordering different_cv_quals(int i, const int j)
+{
+  return partial_order(i, j);
+}
+
+void
+test02()
+{
+  int fortytwo = 42, nines = 999, lots = 1000;
+  VERIFY( different_cv_quals(fortytwo, nines) == partial_ordering::less );
+  VERIFY( different_cv_quals(-nines, -nines) == partial_ordering::equivalent );
+  VERIFY( different_cv_quals(-nines, -lots) == partial_ordering::greater );
+}
+
+void
+test03()
+{
+  double zero = 0.0;
+  VERIFY( partial_order(zero, zero) == partial_ordering::equivalent );
+  VERIFY( partial_order(-zero, -zero) == partial_ordering::equivalent );
+  VERIFY( partial_order(-zero, zero) == partial_ordering::equivalent );
+  VERIFY( partial_order(zero, -zero) == partial_ordering::equivalent );
+  static_assert( noexcept(partial_order(zero, 1.0)) );
+  static_assert( partial_order(0.0, 1.0) == std::partial_ordering::less );
+
+  double min = std::numeric_limits<double>::lowest();
+  double max = std::numeric_limits<double>::max();
+  double nan = std::numeric_limits<double>::quiet_NaN();
+  double inf = std::numeric_limits<double>::infinity();
+  double denorm = std::numeric_limits<double>::denorm_min();
+  double smallest = std::numeric_limits<double>::min();
+  double epsilon = std::numeric_limits<double>::epsilon();
+  VERIFY( partial_order(denorm, smallest) == partial_ordering::less );
+  VERIFY( partial_order(denorm, 0.0) == partial_ordering::greater );
+  VERIFY( partial_order(0.0, nan) == partial_ordering::unordered );
+  VERIFY( partial_order(nan, nan) == partial_ordering::unordered );
+  VERIFY( partial_order(nan, 0.0) == partial_ordering::unordered );
+  VERIFY( partial_order(-nan, 0.0) == partial_ordering::unordered );
+  VERIFY( partial_order(-nan, min) == partial_ordering::unordered );
+  VERIFY( partial_order(-inf, min) == partial_ordering::less );
+  VERIFY( partial_order(-nan, -inf) == partial_ordering::unordered );
+  VERIFY( partial_order(-inf, -nan) == partial_ordering::unordered );
+  VERIFY( partial_order(max, inf) == partial_ordering::less );
+  VERIFY( partial_order(inf, max) == partial_ordering::greater );
+  VERIFY( partial_order(inf, nan) == partial_ordering::unordered );
+  VERIFY( partial_order(1.0, 1.0+epsilon) == partial_ordering::less );
+}
+
+namespace N
+{
+  struct X { int i; };
+
+  constexpr partial_ordering operator<=>(X l, X r)
+  {
+    if (l.i < 0 && r.i < 0)
+      return partial_ordering::equivalent;
+    return r.i <=> l.i;
+  }
+}
+
+void
+test04()
+{
+  using N::X;
+  X one{1};
+  X negone{-1};
+
+  VERIFY( partial_order(one, X{1}) == partial_ordering::equivalent );
+  VERIFY( partial_order(negone, X{-2}) == partial_ordering::equivalent );
+  VERIFY( partial_order(one, X{2}) == partial_ordering::greater );
+  static_assert( !noexcept(partial_order(X{1}, X{2})) );
+}
+
+int main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+}

libstdc++-v3/testsuite/18_support/comparisons/algorithms/strong_order.cc

+// Copyright (C) 2019 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 compile { target c++2a } }
+
+#include <compare>
+#include <limits>
+
+using std::strong_order;
+using std::strong_ordering;
+
+static_assert( strong_order(1, 2) == strong_ordering::less );
+static_assert( strong_order(1, 1) == strong_ordering::equal );
+static_assert( strong_order(2, 1) == strong_ordering::greater );
+static_assert( noexcept(strong_order(1, 1)) );
+
+constexpr strong_ordering different_cv_quals(int i, const int j)
+{
+  return strong_order(i, j);
+}
+static_assert( different_cv_quals(42, 999) == strong_ordering::less );
+static_assert( different_cv_quals(-999, -999) == strong_ordering::equal );
+static_assert( different_cv_quals(-99, -111) == strong_ordering::greater );
+
+namespace N
+{
+  struct X { int i; };
+
+  constexpr strong_ordering operator<=>(X l, X r)
+  {
+    if (l.i < 0 && r.i < 0)
+      return strong_ordering::equivalent;
+    return r.i <=> l.i;
+  }
+}
+using N::X;
+
+static_assert( strong_order(X{1}, X{1}) == strong_ordering::equal );
+static_assert( strong_order(X{-1}, X{-2}) == strong_ordering::equivalent );
+static_assert( strong_order(X{1}, X{2}) == strong_ordering::greater );
+static_assert( !noexcept(strong_order(X{1}, X{2})) );

libstdc++-v3/testsuite/18_support/comparisons/algorithms/weak_order.cc

+// Copyright (C) 2019 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 <compare>
+#include <limits>
+#include <testsuite_hooks.h>
+
+using std::weak_order;
+using std::weak_ordering;
+
+void
+test01()
+{
+  int one = 1, two = 2;
+
+  VERIFY( weak_order(one, two) == weak_ordering::less );
+  VERIFY( weak_order(one, one) == weak_ordering::equivalent );
+  VERIFY( weak_order(two, one) == weak_ordering::greater );
+  static_assert( noexcept(weak_order(1, 1)) );
+}
+
+constexpr weak_ordering different_cv_quals(int i, const int j)
+{
+  return weak_order(i, j);
+}
+
+void
+test02()
+{
+  int fortytwo = 42, nines = 999, lots = 1000;
+
+  VERIFY( different_cv_quals(fortytwo, nines) == weak_ordering::less );
+  VERIFY( different_cv_quals(-nines, -nines) == weak_ordering::equivalent );
+  VERIFY( different_cv_quals(-nines, -lots) == weak_ordering::greater );
+}
+
+void
+test03()
+{
+  double zero = 0.0;
+  VERIFY( weak_order(zero, zero) == weak_ordering::equivalent );
+  VERIFY( weak_order(-zero, -zero) == weak_ordering::equivalent );
+  VERIFY( weak_order(-zero, zero) == weak_ordering::equivalent );
+  VERIFY( weak_order(zero, -zero) == weak_ordering::equivalent );
+
+  double min = std::numeric_limits<double>::lowest();
+  double max = std::numeric_limits<double>::max();
+  double nan = std::numeric_limits<double>::quiet_NaN();
+  double inf = std::numeric_limits<double>::infinity();
+  double denorm = std::numeric_limits<double>::denorm_min();
+  double smallest = std::numeric_limits<double>::min();
+  double epsilon = std::numeric_limits<double>::epsilon();
+  VERIFY( weak_order(denorm, smallest) == weak_ordering::less );
+  VERIFY( weak_order(denorm, 0.0) == weak_ordering::greater );
+  VERIFY( weak_order(0.0, nan) == weak_ordering::less );
+  VERIFY( weak_order(nan, nan) == weak_ordering::equivalent );
+  VERIFY( weak_order(nan, -nan) == weak_ordering::greater );
+  VERIFY( weak_order(-nan, nan) == weak_ordering::less );
+  VERIFY( weak_order(nan, 0.0) == weak_ordering::greater );
+  VERIFY( weak_order(-nan, 0.0) == weak_ordering::less );
+  VERIFY( weak_order(-nan, min) == weak_ordering::less );
+  VERIFY( weak_order(-inf, min) == weak_ordering::less );
+  VERIFY( weak_order(-nan, -inf) == weak_ordering::less );
+  VERIFY( weak_order(-inf, -nan) == weak_ordering::greater );
+  VERIFY( weak_order(max, inf) == weak_ordering::less );
+  VERIFY( weak_order(inf, max) == weak_ordering::greater );
+  VERIFY( weak_order(inf, nan) == weak_ordering::less );
+  VERIFY( weak_order(1.0, 1.0+epsilon) == weak_ordering::less );
+}
+
+namespace N
+{
+  struct X { int i; };
+
+  constexpr weak_ordering operator<=>(X l, X r)
+  {
+    if (l.i < 0 && r.i < 0)
+      return weak_ordering::equivalent;
+    return r.i <=> l.i;
+  }
+}
+
+void
+test04()
+{
+  using N::X;
+  X one{1};
+  X negone{-1};
+
+  VERIFY( weak_order(one, X{1}) == weak_ordering::equivalent );
+  VERIFY( weak_order(negone, X{-2}) == weak_ordering::equivalent );
+  VERIFY( weak_order(one, X{2}) == weak_ordering::greater );
+  static_assert( !noexcept(weak_order(X{1}, X{2})) );
+}
+
+int main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+}