> the one question that matters. Is an executable file with machine code well-defined? While you've insisted that's somehow the one thing which matters I don't

> the one question that matters. Is an executable file with machine code well-defined? While you've insisted that's somehow the one thing which matters I don't agree at all. Are programmers getting paid to produce "any executable file with machine code" ? No. Their employer wanted specific executables which do something in particular. And there aren't "different types of undefined behavior" there's just one Undefined Behaviour. Maybe you've confused it with unspecified behaviour ? In the integer overflow case, because that's UB (in C++) it's very common for the result to be machine code which entirely elides parts which could only happen under overflow conditions. Because overflow is UB that elision didn't change the program meaning and yet it makes the code smaller so that's a win - it didn't mean anything before in this case and it still doesn't - but of course the effect may be very surprising to someone like you. The excuse that "We've done it for decades therefore it can't be a bad idea" shouldn't pass the laugh test. Did you notice you can't buy new lead paint any more? Asbestos pads for ironing boards? Radium dial wristwatches? "That's a bad idea, we shouldn't do that any more" is normal and the reluctance from C++ programmers in particular shows that they're badly out of touch.