I just found that

a: a b: b c: c
   ^ thisContext sender stackPtr

answers 0  :(

while, in order to call the above method , a caller, obviously needs
to push 4 values on stack:
 - push receiver
 - push a
 - push b
 - push c
 - send #a:b:c:

so, a method's caller context stack _should_ contain at least 4 elements.

So, either i wrong, or VM doesn't tracking the context's sp value
correctly anymore.

-- 
Best regards,
Igor Stasenko AKA sig.