This is probably already possible in several language implementations just by telling them to turn off their garbage collector. After all, the essential rule b

This is probably already possible in several language implementations just by telling them to turn off their garbage collector. After all, the essential rule behind garbage collection is that all variables are available to a program for ever - yet the implementation is allowed to clear up memory if it can prove that a value can never be retrieved again (for instance, because all references to it have gone out of scope). It has also crossed my mind that a large number of small, terminating programs might well be better off running to completion without any collection taking place. But language implementors are pretty smart - probably quite a lot of the small programs you have in mind already /do/ run right through without ever doing any garbage collection.