Steven Schveighoffer Wrote: > As long as the spec says changing length may expand the array to hold enough > space, the optimizer can't, because the optimization would change the side > effects of the function. An optimizer should not change the outcome or side > effects of a function. It's not unheard of for an optimizer to eliminate > important operations that it thinks are invalid, but in that case, it's a > broken optimizer, I don't see why we would add this case.
This is all true for user-defined data types, but array is totally under compiler's control. What optimizations are acceptable depends only on the interpretation of the language spec. In particular the sequence a.length -= 1; a.length += 1; as a whole does not result in stomping, so why would it be wrong to optimize it away? I claim it's perfectly legitimate.
