[Bug libstdc++/46914] std::atomic::exchange(...) doesn't store correct value.

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46914

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-01-27 
14:43:49 UTC ---
I think I tried to reproduce it on Fedora last month and failed - I'll look
again at the weekend