It has to be a leaf function or there would be stack frames after, and no local variables after the array, and the function doesn't push anything onto the stack

It has to be a leaf function or there would be stack frames after, and no local variables after the array, and the function doesn't push anything onto the stack, and it has to be possible in ways not covered by tests to actually use that space. Sure, that could happen. But what the other guy was saying about being a compiler developer and being unsure how to calculate the maximum depth is that there are many, many ways to arrive at the wrong result. Resursion, argv/envp, varags, alloca, and so on. So unless you are going to spend a great deal of energy proving maximum depth you're going to be using an estimate of some sort. Thus, 'probably just as good'.