Yes, the optimization assumes that given two pointers to int, either they point to the same int, or they point to distinct, non-overlapping ints. Under that re

Yes, the optimization assumes that given two pointers to int, either they point to the same int, or they point to distinct, non-overlapping ints. Under that restriction the result is guaranteed to be 1. It's allowed to do so by the standard because those are the rules. C was portable assembly back in the early 1980s. The result was that it was crushed in performance by Fortran for scientific codes, and most of the difference had to do with assumptions the compiler could make about aliasing (or the lack of it). This was fixed by the first ANSI C standard (finalized in 1989). Yet I still see people who weren't even born then, or were young children then, talk as if C is supposed to be "portable assembly". It isn't.