[Bug c++/54972] O2 breaks something in 4.6.3

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54972

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-18 12:01:22 UTC ---
(In reply to comment #4)
> You need -Wstrict-aliasing=2. 

And -O2

If the optimization passes don't run then they can't produce warnings.