[alex7734]

To do that you either need a structure that you update every time a pointer is created, copied, moved or deleted (too much overhead), or you need a way to scan the entire memory and get all the pointers. And at the point where you have a piece of code that knows where every pointer is, you already know which pointers aren't used anywhere anymore so it's a waste to not have it also call free() for you.

Once you have it call free() for you, your piece of code is now a compacting GC, like Java's for example.