Question

Suppose I have the following code:

class a {
public:
    virtual void do_a() = 0;
}

class b {
public:
    virtual void do_b() = 0;
}

class c: public a, public b {
public:
    virtual void do_a() {};
    virtual void do_b() {};
}

a *foo = new c();
b *bar = new c();

Will foo->do_a() and bar->do_b() work? What’s the memory layout here?

Answer 1

Why shouldn’t they? The memory layout will typically be something like:

+----------+
|  A part  |
+----------+
|  B part  |
+----------+
|  C part  |
+----------+

If you convert your foo and bar to void* and display them, you’ll
get different addresses, but the compiler knows this, and will arrange
for the this pointer to be correctly fixed up when calling the
function.