In the uncommon case, some stack frames must be heap allocated.
This is unavoidable when (a) the runtime enviroment, here the JVM, does not support tail calls, and (b) the language wants to guarantee that _any_[1] tail call does not grow the stack.
[1] Any call. Not just a call to the same function.
This is unavoidable when (a) the runtime enviroment, here the JVM, does not support tail calls, and (b) the language wants to guarantee that _any_[1] tail call does not grow the stack.
[1] Any call. Not just a call to the same function.