c++ - Check if a pointer is NULL after it's object is deleted in other pointer -

i have simple problem this!

class1 *a = new class1(); class1 *b = a;  delete a; a= null; 

now want check if b null (or deleted) also, b point point previously. problematic when want use b, deleted before!

if (b){     //do here } 

thanks reading!

as have suggested, using shared pointer make easier.

if want raw way, here why *b still points original value of a

when class1 *b=a taking copy of pointer value of a. regardless of a itself, b hangs on original value.

if wanted change along a, need assign reference a, or pointer a pointer

class1 **b = &a; 

so now, think happens when dereference b, value pointing to?

it point original class1 *. so, once set a=null, have pointer b points value of a, or null