vtbl jamming

[Kirk McDonald]

Vladimir Panteleev wrote:
> On Mon, 10 Sep 2007 09:40:59 +0300, BCS <ao at pathlink.com> wrote:
> 
> 
>> can we get some way to do this?
>> 
>> http://www.artima.com/cppsource/backyard2.html
> 
> 
> Modifying VTBLs is effectively the same as using method pointers (as
> a static field). The advantage is when we don't have access to the
> base class. Of course, D doesn't have method pointers (like C++),
> so...
> 

It sort of does. You can fake them with delegates:

class Foo {
     void bar() { writefln("Foo.bar"); }
}

void ptr_call(void function() fn, Object o) {
     void delegate() dg;
     dg.ptr = o;
     dg.funcptr = fn;
     dg();
}

void main() {
     auto f = new Foo;
     void function() fn = &Foo.bar;
     ptr_call(fn, f);
}

I write this without testing it, and may have left out a cast or two. 
But the idea is sound. (Indeed, Pyd relies on it.)

-- 
Kirk McDonald
http://kirkmcdonald.blogspot.com
Pyd: Connecting D and Python
http://pyd.dsource.org