Dereferencing NULL Pointer, without a Seg Fault

Re:Dereferencing NULL Pointer, without a Seg Fault by prophetjohn on Wednesday July 11, 2012 @12:04AM (#4227671)

This reminds me of a conversation I had with a coworker recently about how possible it would be a for an object to check itself for null. Based on this explanation, it seems like this would definitely be possible in C++ (our conversation was in the context of Java, but it's interesting from an academic perspective)

    class NullChecker {
    public:
      bool isNull() { return !!this; }
    };

    int main() {
      NullChecker *nc = 0;
      if(nc->isNull()) doSomething();
      return 0;
    }

Forgive my C++ syntax as it's been a while, but this seems like it would work to me.

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Re:Dereferencing NULL Pointer, without a Seg Fault by z92 on Wednesday July 11, 2012 @02:18AM (#4228016)

Tried it. It works.

Technically I look at methods as functions with a hidden first parameter that accepts a pointer to the class object's data. If you don't try to dereference that pointer, then the function should work like static member.

I was wondering if the compiler will add some check code preventing me from calling any method on a NULL pointed obj. But obviously its permitting it.

Of course virtual methods are different. Then you are calling a pointer to a function, the address of which should be stored in your obj data structure.

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