[Bug libstdc++/49559] [C++0x] stable_sort calls self-move-assignment operator

["paolo.carlini at oracle dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49559

--- Comment #12 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-06-28 18:06:54 UTC ---
I'm looking at __merge_adaptive and it seems to me that self move assignment
can happen very generically. Consider:

 if (__len1 <= __len2 && __len1 <= __buffer_size)
   {
     _Pointer __buffer_end = _GLIBCXX_MOVE3(__first, __middle, __buffer);
     std::__move_merge(__buffer, __buffer_end, __middle, __last, __first);
   }

here __first comes in memory before __middle and when __move_merge has filled
all the positions before __middle then any element can be move assigned from
itself. Of course we could always move to the buffer the entire range __first,
__last. Still looking for Chris' opinion on this, he updated this code to move
instead of copy...