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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/59603] std::random_shuffle tries to swap element with itself
Date: Sat, 08 Feb 2014 20:19:00 -0000 [thread overview]
Message-ID: <bug-59603-4-ft6Rt9xoof@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-59603-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59603
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This patch avoids the self-move:
index 4c6ca8a..6ce2d21 100644
--- a/libstdc++-v3/include/bits/stl_algo.h
+++ b/libstdc++-v3/include/bits/stl_algo.h
@@ -4430,7 +4430,12 @@ _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)));
+ {
+ int __offset = std::rand() % ((__i - __first) + 1);
+ _RandomAccessIterator __j = __first + __offset;
+ if (__i != __j)
+ std::iter_swap(__i, __j);
+ }
}
/**
But I'm not sure whether this is a real bug, or types used with random_shuffle
should be safe against self-move (which means they can't use an implicit move
ctor if they have types that are not safe against self-move, which includes
most std::lib types).
next prev parent reply other threads:[~2014-02-08 20:19 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-26 16:36 [Bug libstdc++/59603] New: " fab at orlen dot de
2013-12-26 16:37 ` [Bug libstdc++/59603] " fab at orlen dot de
2014-02-04 8:38 ` joerg.richter@pdv-fs.de
2014-02-04 13:10 ` redi at gcc dot gnu.org
2014-02-08 20:19 ` redi at gcc dot gnu.org [this message]
2014-02-09 17:31 ` joerg.richter@pdv-fs.de
2014-02-10 19:00 ` redi at gcc dot gnu.org
2014-09-12 11:45 ` redi at gcc dot gnu.org
2014-09-12 13:31 ` redi at gcc dot gnu.org
2014-09-12 13:35 ` redi at gcc dot gnu.org
2014-12-06 20:38 ` redi at gcc dot gnu.org
2014-12-06 22:04 ` redi at gcc dot gnu.org
2015-09-16 11:37 ` TonyELewis at hotmail dot com
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