On a system where the data space grows dynamically, there is no inherent compile-time limit on the maximum address in data space, and there might be no easy way to probe at runtime how large of an address can be allocated without failure. In that scenario, is it better to include the word UNUSED and have it return -1 to indicate unknown (or rather, the maximum unsigned integer since the prototype uses 'u'), or to omit the word UNUSED from the core extension set? Some traditional systems had...
