Using the heap to store stack traces when TCO is in use and a "debugging" flag is set won't work. It could cause memory to be exhausted. You're effectively ca

Using the heap to store stack traces when TCO is in use and a "debugging" flag is set won't work. It could cause memory to be exhausted. You're effectively causing each recursion to consume memory; something TCO is trying to avoid. If the coder assumes TCO then they could have written code which will exhaust memory once the "debugging flag" starts storing stack trace information.