Calling class method through NULL class pointer [duplicate]

Answer 1

This one will explain you more than if I use plain words. Try compiling it with any compiler you want :) But note, it's UB according to standards!

#include 
using namespace std;

class Armor
{
public:
    void set(int data)
    {
        cout << "set("<data = data;  //dereference it here
    }
    void get()
    {
        if(this) cout << "data = " << data << "\n";
        else cout << "Trying to dereference null pointer detected!\n";
    }
    int data;
};

int main()
{
   cout << "Hello World" << endl; 
   Armor a;
   a.set(100);
   a.get();


   Armor* ptr1 = &a;
   Armor* ptr2 = 0;

   ptr1->set(111);
   ptr2->set(222);

   ptr1->get();
   ptr2->get();

   return 0;
}

Then read about __thiscall - and all comments above.

Hello World
set(100)
data = 100
set(111)
set(222)
I am called on NULL object! I prefer to not crash!
data = 111
Trying to dereference null pointer detected!