Fix value category bugs in std::reduce

	* include/std/numeric (reduce(Iter, Iter, T, BinOp)): Fix value
	category used in invocable check.
	(reduce(Iter, Iter, T)): Pass initial value as rvalue.
	* testsuite/26_numerics/reduce/2.cc: New test.

From-SVN: r272477

3 files changed, 79 insertions, 2 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 5702523..e6373ca 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2019-06-19  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/numeric (reduce(Iter, Iter, T, BinOp)): Fix value
+	category used in invocable check.
+	(reduce(Iter, Iter, T)): Pass initial value as rvalue.
+	* testsuite/26_numerics/reduce/2.cc: New test.
+
 2019-06-18  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/algorithmfwd.h: Change title of doc group.
diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric
index 6679250..fc2242f 100644
--- a/libstdc++-v3/include/std/numeric
+++ b/libstdc++-v3/include/std/numeric
@@ -246,7 +246,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	   _BinaryOperation __binary_op)
     {
       using value_type = typename iterator_traits<_InputIterator>::value_type;
-      static_assert(is_invocable_r_v<_Tp, _BinaryOperation, _Tp&, _Tp&>);
+      static_assert(is_invocable_r_v<_Tp, _BinaryOperation&, _Tp&, _Tp&>);
       static_assert(is_convertible_v<value_type, _Tp>);
       if constexpr (__is_random_access_iter<_InputIterator>::value)
 	{
@@ -278,7 +278,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _InputIterator, typename _Tp>
     inline _Tp
     reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
-    { return std::reduce(__first, __last, __init, plus<>()); }
+    { return std::reduce(__first, __last, std::move(__init), plus<>()); }
 
   /**
    *  @brief  Calculate reduction of values in a range.
diff --git a/libstdc++-v3/testsuite/26_numerics/reduce/2.cc b/libstdc++-v3/testsuite/26_numerics/reduce/2.cc
new file mode 100644
index 0000000..adbfaf8
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/reduce/2.cc
@@ -0,0 +1,70 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+// 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/>.
+
+// C++17 29.8.3 [reduce]
+
+#include <numeric>
+#include <iterator>
+#include <testsuite_hooks.h>
+#include <testsuite_iterators.h>
+
+struct T
+{
+  T(int);
+  T(T&&); // MoveConstructible
+  T& operator=(T&&); // not required by the standard, but it needs to be
+  T operator+(const T&) const;
+};
+
+void
+test01()
+{
+  T t[1]{1};
+  std::reduce(t, t+1, T(0));
+
+  using __gnu_test::test_container;
+  using __gnu_test::input_iterator_wrapper;
+  test_container<T, input_iterator_wrapper> con(t);
+  std::reduce(con.begin(), con.end(), T(0));
+}
+
+struct Op
+{
+  T operator()(T&, T&) const&;
+
+  // The standard does *not* require invoking as an rvalue to be supported.
+  T operator()(T&, T&) && = delete;
+
+  // The standard does *not* require rvalue arguments to be supported
+  // (this is almost certainly a defect and should be allowed).
+  T operator()(T&&, T&&) const = delete;
+};
+
+void
+test02()
+{
+  T t[1]{1};
+  std::reduce(t, t+1, T(0), Op());
+
+  using __gnu_test::test_container;
+  using __gnu_test::input_iterator_wrapper;
+  test_container<T, input_iterator_wrapper> con(t);
+  std::reduce(con.begin(), con.end(), T(0), Op());
+}