crystal clear()

[Andrei Alexandrescu]

On 09/17/2010 05:30 PM, Sean Kelly wrote:
> Steven Schveighoffer Wrote:
>>
>> But here is a legitimate question, how do we get the interfaces?  There's
>> no indication in the ABI of where the interfaces are.  I know from logic
>> that they must be before the data members.  But logic also says that
>> interfaces defined by the derived types must appear after the data members
>> of the base class.  This is indeed tricky.
>
> I'd guess that the interface vtbls are referenced from the class vtbl, so clearing the vptr should wipe everything.

Actually, casting to an interface adds a constant offset to the pointer 
to the object without using the vptr at all. The shared referencing you 
might be thinking about is the actual function addresses: portions of 
the main vtable are identical with the interfaces vtables.

So you'll have an odd object that still kind of works when invoked 
through an interface...

Andrei