[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 #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-18 11:31:59 UTC ---
Apparently you didn't read http://gcc.gnu.org/bugs/

   Before reporting that GCC compiles your code incorrectly,
   compile it with gcc -Wall -Wextra and see whether this shows
   anything wrong with your code. Similarly, if compiling with
   -fno-strict-aliasing -fwrapv makes a difference, your code
   probably is not correct.

And also the section on "Casting does not work as expected when optimization is
turned on" at http://gcc.gnu.org/bugs/#nonbugs

You should never report a bug without turning on warnings and seeing if the
compiler can tell you where the problem is.