[Bug c++/46246] [C++0x] Move constructor required when passing a temporary by copy, but not actually used

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46246

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-10-31 
12:05:00 UTC ---
Copy elision is an optimisation allowed by the standard, but not mandated.

-fno-elide-constructors to disable it, then you should see the move constructor
called for the second test case.

The relevant constructor must be accessible and callable even if it is elided.