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

Although in the standards dereferencing a zero pointer (NULL) is undefined behavior, current processors and operating systems generate a segmentation fault or similar error.

Maybe that function you called accepts a reference parameter (which IS a pointer) and that function doesn't use the paramenter, so the NULL won't be dereferenced.