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re PR libstdc++/59603 (std::random_shuffle tries to swap element with itself) 

PR libstdc++/59603
	* include/bits/stl_algo.h (random_shuffle): Prevent self-swapping.
	* testsuite/25_algorithms/random_shuffle/59603.cc: New.

From-SVN: r215219
This commit is contained in:
Jonathan Wakely 2014-09-12 14:30:35 +01:00 committed by Jonathan Wakely
parent 139c9e3b9b
commit bc5022d011
3 changed files with 52 additions and 2 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
2014-09-12 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/59603
* include/bits/stl_algo.h (random_shuffle): Prevent self-swapping.
* testsuite/25_algorithms/random_shuffle/59603.cc: New.
2014-09-11 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/63219

14
libstdc++-v3/include/bits/stl_algo.h
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@ -4430,7 +4430,13 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
if (__first != __last)
for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
std::iter_swap(__i, __first + (std::rand() % ((__i - __first) + 1)));
{
// XXX rand() % N is not uniformly distributed
_RandomAccessIterator __j = __first
+ std::rand() % ((__i - __first) + 1);
if (__i != __j)
std::iter_swap(__i, __j);
}
}
/**
@ -4464,7 +4470,11 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
if (__first == __last)
return;
for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
std::iter_swap(__i, __first + __rand((__i - __first) + 1));
{
_RandomAccessIterator __j = __first + __rand((__i - __first) + 1);
if (__i != __j)
std::iter_swap(__i, __j);
}
}

34
libstdc++-v3/testsuite/25_algorithms/random_shuffle/59603.cc Normal file
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@ -0,0 +1,34 @@
// Copyright (C) 2014 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++11" }
// { dg-require-debug-mode "" }
// libstdc++/59603
#include <algorithm>
#include <vector>
struct C {
std::vector<int> v;
C (int a) : v{a} {};
};
int main () {
std::vector<C> cs { {1}, {2}, {3}, {4} };
std::random_shuffle(cs.begin(), cs.end());
}