Have I found a black hole in C++?

[vronin]

Here some stuff which I did in Visual Studio 2005 and CodeWarrior.
So, it's definitelly not a jsut compiler bug.

I defined class like this:

class A
{
public:
	virtual void B() = 0;
};

So, I have pure virtual method.
Sure thing, we can't instantiate class.

However, what I found I can add implementation for pure virtual method (which doesn't make any sense)

void A::B()
{
	printf("z");
}

And compiler won't say me a damn thing.
I can't instantiate it still.

However, I can do this:

class C: public A
{
public:
	virtual void B();
};

void C::B()
{
	A::B();
}

First of all I was able to compile this, where I can pure abstract method.
Second, I was able to debug it and step into A::B.

It's definitelly crazy.

Does anybody have explanation, why it works?