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[google] Fix PR52822 in google's gcc-4.6 branch (issue5975063)


I'll send the patches for trunk, gcc-4_7-branch, and gcc-4_6-branch in
a separate thread later today or tomorrow, but I need to get the
google branch fixed before that. Paolo suggested this simple fix was
the right approach for the gcc-4_6-branch, so I'm using it for
google/gcc-4_6 too. I'll be happy to fix up the google branch to match
whatever gets accepted for gcc-4_6-branch once that's decided.

Tested with `make check` on x86-64-linux, and I'll check this against
the build I originally noticed the problem in before committing it.

2012-04-02   Jeffrey Yasskin  <jyasskin@google.com>

	* libstdc++-v3/include/bits/stl_algo.h (__stable_partition_adaptive):
        Avoid move-assigning an object to itself by explicitly testing
        for identity.
	* libstdc++-v3/testsuite/25_algorithms/stable_partition/pr52822.cc:
        Test vectors, which have a destructive self-move-assignment.
	* libstdc++-v3/testsuite/25_algorithms/stable_partition/moveable.cc (test02):
        Test with rvalstruct, which explicitly checks self-move-assignment.

Index: libstdc++-v3/include/bits/stl_algo.h
===================================================================
--- libstdc++-v3/include/bits/stl_algo.h	(revision 186093)
+++ libstdc++-v3/include/bits/stl_algo.h	(working copy)
@@ -1844,7 +1844,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  for (; __first != __last; ++__first)
 	    if (__pred(*__first))
 	      {
-		*__result1 = _GLIBCXX_MOVE(*__first);
+                if (&*__result1 != &*__first)
+                  *__result1 = _GLIBCXX_MOVE(*__first);
 		++__result1;
 	      }
 	    else
Index: libstdc++-v3/testsuite/25_algorithms/stable_partition/pr52822.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/stable_partition/pr52822.cc	(revision 0)
+++ libstdc++-v3/testsuite/25_algorithms/stable_partition/pr52822.cc	(revision 0)
@@ -0,0 +1,43 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2012 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 Pred 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/>.
+
+// 25.2.12 [lib.alg.partitions] Partitions.
+
+#include <algorithm>
+#include <vector>
+#include <testsuite_hooks.h>
+
+bool true_vector_pred(const std::vector<int>&) { return true; }
+
+void
+test01()
+{
+  std::vector<std::vector<int> > v(1);
+  v[0].push_back(7);
+  VERIFY( v[0].size() == 1 );
+  std::stable_partition(v.begin(), v.end(), &true_vector_pred);
+  VERIFY( v[0].size() == 1 );
+}
+
+int
+main()
+{
+  test01();
+  return 0;
+}
Index: libstdc++-v3/testsuite/25_algorithms/stable_partition/moveable.cc
===================================================================
--- libstdc++-v3/testsuite/25_algorithms/stable_partition/moveable.cc	(revision 186093)
+++ libstdc++-v3/testsuite/25_algorithms/stable_partition/moveable.cc	(working copy)
@@ -1,6 +1,6 @@
 // { dg-options "-std=gnu++0x" }
 
-// Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+// Copyright (C) 2009, 2010, 2012 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
@@ -39,6 +39,12 @@ const int A[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
 const int B[] = {2, 4, 6, 8, 10, 12, 14, 16, 1, 3, 5, 7, 9, 11, 13, 15, 17};
 const int N = sizeof(A) / sizeof(int);
 
+// Check that starting with a value the predicate returns true for
+// works too. (PR52822)
+const int A2[] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17};
+const int B2[] = {2, 4, 6, 8, 10, 12, 14, 16, 3, 5, 7, 9, 11, 13, 15, 17};
+const int N2 = sizeof(A2) / sizeof(int);
+
 struct Pred
 {
   bool
@@ -46,7 +52,8 @@ struct Pred
   { return (x.val % 2) == 0; }
 };
 
-// 25.2.12 stable_partition()
+// 25.2.12 stable_partition(), starting with a value for which the
+// predicate returns false.
 void
 test01()
 {
@@ -60,9 +67,25 @@ test01()
   VERIFY( std::equal(s1, s1 + N, B) );
 }
 
+// 25.2.12 stable_partition(), starting with a value for which the
+// predicate returns true.
+void
+test02()
+{
+  bool test __attribute__((unused)) = true;
+
+  rvalstruct s1[N2];
+  std::copy(A2, A2 + N2, s1);
+  Container con(s1, s1 + N2);
+
+  std::stable_partition(con.begin(), con.end(), Pred());
+  VERIFY( std::equal(s1, s1 + N2, B2) );
+}
+
 int
 main()
 {
   test01();
+  test02();
   return 0;
 }

--
This patch is available for review at http://codereview.appspot.com/5975063


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