"Safe" pointer values interval?

Question

First of all I am not very familiar with the stack and heap.

In a lot of programs I see that pointers are checked for NULL. But that doesn't prevent a crazy address like 0x002011 to be passed.

My question: is there "safe" address interval, that I can check a pointer belongs to and be reasonably sure it's valid, before dereferencing it?

Answer 1

No. Make sure to initialize pointers to NULL when creating a new variable, and then only change the value with malloc (when C) or new (when C++) or other allocating functions (or assigning to another valid pointer or NULL). Set back to NULL after free and delete respectively.