What part of dereferencing NULL pointers causes undesired behavior?

Question

I am curious as to what part of the dereferencing a NULL ptr causes undesired behavior. Example:

//  #1
someObj * a;
a = NULL;
(*a).somefunc();   // crash, dere         


        

Answer 1

NULL is just 0. Since 0 doesn't point to a real memory address, you can't dereference it. *b can't just resolve to NULL, since NULL is something that applies to pointers, not objects.