My original test case passes with this change.

On Mon, Apr 2, 2012 at 3:25 PM, Jeffrey Yasskin <jyass...@google.com> wrote:
> 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  <jyass...@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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