You pulled that from the UCLA site, which is the microcontroller version from 15 years ago. That version actually burned the entire heap into the binary and did

You pulled that from the UCLA site, which is the microcontroller version from 15 years ago. That version actually burned the entire heap into the binary and did not allow dynamic allocation. In that case, no GC, write barriers, allocation, etc was necessary. Today's Virgil (on GitHub) does allow dynamic allocation, but you can still initialize an arbitrarily large heap at compile time. It's not really related to ARC.