For the regex problem, because of the required backtracking, data usage is definitely not O(1), so the continuation data will not be storable on the stack for an O(1) stack tail-call-only CPS version of regex. That context data for the continuations will need to go to the heap, and so we are basically back to how you'd avoid recursion to avoid unbounded stack: by using some data structures on the heap. And at that point, you could just use more straight-forward data structures than those needed for CPS here.
Anyway, the one-phase parsing+matching is still interesting, I think, and it is worth a try to get it to work in O(1) stack by storing the continuation data on the heap. So after fixing SIGSEGVs for infinite recursions, I will go back to fixing memory leaks. :-)
For the regex problem, because of the required backtracking, data usage is definitely not O(1), so the continuation data will not be storable on the stack for an O(1) stack tail-call-only CPS version of regex. That context data for the continuations will need to go to the heap, and so we are basically back to how you'd avoid recursion to avoid unbounded stack: by using some data structures on the heap. And at that point, you could just use more straight-forward data structures than those needed for CPS here.
Anyway, the one-phase parsing+matching is still interesting, I think, and it is worth a try to get it to work in O(1) stack by storing the continuation data on the heap. So after fixing SIGSEGVs for infinite recursions, I will go back to fixing memory leaks. :-)