@lanodan @ipg @halva You don't have to make the core in C and there are quite a few self-hosted languages that don't.

Linux has a stable ABI for userspace (mostly), so it is possible to even do the whole thing from scratch and communicating directly with the system that way, skipping C entirely. In general instead such languages deem it simpler to make a C wrapper which can communicate with their own ABI instead.