== for pointer comparison

Question

I quote from \"The C Programming Language\" by Kernighan & Ritchie:

Any pointer can be meaningfully compared for equality or inequality with zero.

Answer 1

One example that comes to my mind is Harvard architecture with separate address spaces for code and for data. In computers of that architecture the compiler can store constant data in the code memory. Since the two address spaces are separate, a pointer to an address in the code memory could be numerically equal to a pointer in the data memory, without pointing to the same address.