In our example here the argument `pfds` to the addition operator in the expression `pfds + p` is (presumably) a perfectly valid pointer. And `p` is a perfectly

In our example here the argument `pfds` to the addition operator in the expression `pfds + p` is (presumably) a perfectly valid pointer. And `p` is a perfectly valid `int`. So there are no invalid pointers passed as arguments to the addition operation. You might think the result of the addition expression is an invalid pointer, but the result is simply undefined behaviour. Typically an invalid pointer is created by deallocating some memory, which transforms previously valid pointers to the memory into invalid pointers without the pointer values themselves changing their value.