I would also mention https://github.com/edef1c/libfringe https://github.com/edef1c/libfringe which pretty much solves context-switches (by replacing them with c

I would also mention https://github.com/edef1c/libfringe https://github.com/edef1c/libfringe which pretty much solves context-switches (by replacing them with compiler-generated minimal stack spills/restores). But as you might be able to tell from their APIs, you still have to allocate stacks somehow.