It would be non-conforming for a const pointer to use a different representation than a non-const pointer. 6.2.5 p28 sentence 2 says "Similarly, pointers to qualified or unqualified versions of compatible types shall have the same representation and alignment requirements." I could imagine a system that wants to do this, like a Harvard architecture to be able to specify code/data memories for const pointers, but the standard also allows ANY const pointer to be converted to a non-const pointer, and be fully usable as long as you don't actually write through it, so those platforms really need other solutions.