How interesting! I thought that setjmp and longjmp were probably incompatible with Fil-C. And I'd somehow never heard of ucontext at all.

I suppose managing the stack is still managing memory after all, even if we typically don't think of it that way, so Fil-C has something to add here.

It's really worth reading the section here about the complexity of setjmp/longjmp and how they interact with register allocation and stack spilling. I knew they're tricky, but going in to the specifics is delicious.