What if the implementation handles dereferences of invalid pointers by accessing the value at the corresponding address, and all possible addresses are all vali

What if the implementation handles dereferences of invalid pointers by accessing the value at the corresponding address, and all possible addresses are all valid? (I have worked on a system that worked liked this. There was some kind of process information block at address 0, and NULL at runtime was all bits reset. The system compiler was not gcc.)