[astrange]

In reality I'm not sure what kind of loop would have an index only fitting in an unsigned type.

On a 32-bit machine an unsigned array index means one object using more than half the address space. It's sensible to use unsigned 64-bit for file sizes, but I think it's quite odd that C programers would use it for a loop or array index. Wrong, but defined, behavior is worse than undefined behavior, you know.

On a 64-bit machine, well, it shouldn't be a problem to use signed long long.