Comment 6 for bug 1196251

gcc developer says gcc 4.8 does this type of "aggressive optimization" when loop contains undefined behavior, ref:

http://gcc.gnu.org/gcc-4.8/porting_to.html
https://lists.fedoraproject.org/pipermail/devel/2013-January/175876.html

i.e. loop may be "optimized" into endless loop.

By the way, I have sent the same patch to the upstream, which was accepted on 2013-06-10.