@jdent
As @Christian-Ehrlicher says, who knows, behaviour may be compiler-specific and it does not claim to check everything, I think. My own guess is that the call to showing the dialog avoiding the detection may well be "coincidence", nothing to do with the specific call, many other things might cause it to skip.
Under Ubuntu, Qt 5, gcc and .pro file having
CONFIG+=sanitizer
CONFIG+=sanitize_address
it does report a SIGABRT on code like yours, whether I put in a QDialog and/or exec() or not. I do not know whether you can use those CONFIG lines from Qt with MSVC or not.
One tiny thing: just in case MSVC is "optimizing out" your x code completely because it has no effect (e.g. gcc warns "unused variable"), add something which uses x after your code.
