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From: "fab at orlen dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/59603] New: std::random_shuffle tries to swap element with itself
Date: Thu, 26 Dec 2013 16:36:00 -0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Version: 4.8.2
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: fab at orlen dot de
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59603

            Bug ID: 59603
           Summary: std::random_shuffle tries to swap element with itself
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fab at orlen dot de

When using the debugging macro _GLIBCXX_DEBUG, calling random_shuffle fails on
some types, because it might try to swap an element with itself.

Output of attached program:

/tmp$ g++ -o random_shuffle_bug -std=c++11 random_shuffle_bug.cc 
/tmp$ ./random_shuffle_bug 
/usr/include/c++/4.8.2/debug/vector:159:error: attempt to self move assign.

Objects involved in the operation:
sequence "this" @ 0x0xa600c8 {
  type = NSt7__debug6vectorIiSaIiEEE;
}
Aborted (core dumped)

return code: 134

I could not find any information about whether swapping an element with itself
is allowed.