Question

In C++ do you always have to initialize a pointer to an object with the new keyword?

Or can you just have this too:

MyClass *myclass;

myclass->DoSomething();

I thought this was a pointer allocated on the stack instead of the heap, but since objects are normally heap-allocated, I think my theory is probably faulty?

Please advice.

Answer 1

No, you can have pointers to stack allocated objects:

MyClass *myclass;
MyClass c;
myclass = & c;
myclass->DoSomething();

This is of course common when using pointers as function parameters:

void f( MyClass * p ) {
    p->DoSomething();
}

int main() {
    MyClass c;
    f( & c );
}

One way or another though, the pointer must always be initialised. Your code:

MyClass *myclass;
myclass->DoSomething();

leads to that dreaded condition, undefined behaviour.