re PR libstdc++/58800 (std::nth_element segfaults on valid input)

2013-10-20  Chris Jefferson  <chris@bubblescope.net>
	    Paolo Carlini  <paolo.carlini@oracle.com>

	PR libstdc++/58800
	* include/bits/stl_algo.h (__unguarded_partition_pivot): Change
	__last - 2 to __last - 1.
	* testsuite/25_algorithms/nth_element/58800.cc: New

Co-Authored-By: Paolo Carlini <paolo.carlini@oracle.com>

From-SVN: r203872

libstdc++-v3/ChangeLog

+2013-10-20  Chris Jefferson  <chris@bubblescope.net>
+	    Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR libstdc++/58800
+	* include/bits/stl_algo.h (__unguarded_partition_pivot): Change
+	__last - 2 to __last - 1.
+	* testsuite/25_algorithms/nth_element/58800.cc: New
+
 2013-10-18  Edward Smith-Rowland  <3dw4rd@verizon.net>
 
 	PR libstdc++/58729

libstdc++-v3/include/bits/stl_algo.h

@@ -1917,7 +1917,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 				_RandomAccessIterator __last, _Compare __comp)
     {
       _RandomAccessIterator __mid = __first + (__last - __first) / 2;
-      std::__move_median_to_first(__first, __first + 1, __mid, (__last - 2),
+      std::__move_median_to_first(__first, __first + 1, __mid, __last - 1,
 				  __comp);
       return std::__unguarded_partition(__first + 1, __last, __first, __comp);
     }

libstdc++-v3/testsuite/25_algorithms/nth_element/58800.cc

+// Copyright (C) 2013 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/>.
+
+// 25.3.2 [lib.alg.nth.element]
+
+// { dg-options "-std=gnu++11" }
+
+#include <algorithm>
+#include <testsuite_hooks.h>
+#include <testsuite_iterators.h>
+
+using __gnu_test::test_container;
+using __gnu_test::random_access_iterator_wrapper;
+
+typedef test_container<int, random_access_iterator_wrapper> Container;
+
+void test01()
+{
+  std::vector<int> v = {
+    207089,
+    202585,
+    180067,
+    157549,
+    211592,
+    216096,
+    207089
+  };
+
+  Container con(v.data(), v.data() + 7);
+
+  std::nth_element(con.begin(), con.begin() + 3, con.end());
+}
+
+int main()
+{
+  test01();
+  return 0;
+}