It is nothing short of sheer hubris to believe that you have avoided all undefined behavior, particularly given that there exist undefined behaviors that have no extant static or dynamic checkers (hi, strict aliasing).

I do know the strict aliasing rules quite well. As I said in a cousin post, the set of permissible accesses to a lvalue are governed by the dynamic type of an object. As a consequence, strict aliasing queries are not symmetric, which is to say, P* could point to an object of type Q* but not vice versa. The case where this will come up is with signed/unsigned char. If you have a char foo[]; as the dynamic object, it is positively illegal to access that with anything other than unsigned or signed char. This is what really screws up a lot of code.