Uninitialized pointer and member functions

A very unpleasant scenario possible when you forget to initialize a pointer to a class. Let's say, we have class CBase with a member function which doesn't use member data, i.e. it doesn't need this pointer.

class CBase
{
    int i;
public:
    void f() { std::cout<<"CBase::f"<<std::endl;}
};

And after that you write the following code somewhere:

CBase* p = NULL;
p->f();

This is an undefined behavior by the Standard. But sometimes it works. Visual Studio 2008, for example, generates a working code. The function call is resolved during the compilation, we don't use this. And you remain oblivious for a long period of time. Here is a scarier looking example

((CBase*)0)->f();

But when you try to use this pointer, you program "crashes". Examples:

class CBase
{
    int i;
public:
    virtual void f() { std::cout<<"CBase::f"<<std::endl;}
};

class CBase
{
    int i;
public:
    void f() { std::cout<<"CBase::f"<<std::endl; i=0;}
};

All this leads to very interesting, hard to find bugs.

Links:
comp.lang.c++.moderated - Functions that don't use this, called with uninitialized pointers