CPS-cps recursion leads to stack overflow

[Ico Doornekamp]

Can we TCO this somehow?

import cps          
            
type C = ref object of Continuation

proc child() {.cps:C.} =
  echo "Child"
             
proc parent() {.cps:C.} =
  echo "Parent 1"
  child()
  echo "Parent 2"
  parent()
  
var c: C = whelp parent()   

while c.running: 
  c = C(c.fn(c))

...
/tmp/t.nim(9)            parent
/home/ico/sandbox/prjs/cps/cps/spec.nim(231) trampoline
/tmp/t.nim(13)           Post Call
/tmp/t.nim(9)            parent
/home/ico/sandbox/prjs/cps/cps/spec.nim(231) trampoline
/home/ico/sandbox/prjs/cps/cps/transform.nim(902) parent_385876580
/home/ico/sandbox/prjs/cps/cps/transform.nim(884) whelp
/home/ico/sandbox/prjs/cps/cps.nim(210) alloc
/home/ico/external/Nim/lib/system.nim(902) new
/home/ico/external/Nim/lib/system/gc.nim newObj
Error: call depth limit reached in a debug build (2000 function calls). You can change it with -d:nimCallDepthLimit=<int> but really try to avoid deep recursions instead.

[alaviss]

TCO will come, but the issue here is not that. What happened was that since the proc wasn't tagged with any cps data, we don't know that we should perform a jump like it was a cps proc.