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

It would still cause a crash, but that's not necessarily undesired behaviour. Part of the usefulness of NULL is that, on most platforms, it points to memory that is explicitly inaccessible to your application, and causes a segmentation fault (or access violation) the very moment you try to dereference it.

Its purpose is to explicitly mark the contents of pointers as invalid.