in case the value of 0 changes, perhaps on a machine with nonzero no-op instructions?
No. The ‘0’ of ‘0;’ is not evaluated as an instruction, rather, it is just ignored. The only reason to use ‘0;’ instead of ‘;’ is to help keep 1-heavy code properly balanced (in C, which uses binary representations for numbers, it is possible for code to become unbalanced; an unbalanced binary tree is a common source of poor performance.
