Re: abstract sub programs overriding

[Hyman Rosen <hyrosen@mail.com>]

Robert I. Eachus wrote:
> If you look at what I was talking about

I think I still don't understand. If you say 'a := b;' and a has a
Controlled type, isn't Finalize called on a before its bits are
clobbered? So in your Initilaize example, when you say
'Object := (Parent_Type with ...);', isn't Finalize called on Object
before its bits are replaced with the extension aggregate? And since
we're in the first Initialize of Object, doesn't that mean that Finalize
will be called on it before its first Initialize is complete?

> However if the Initialize for the parent type is called by the 
> Initialize for the child type, and you do this, it is the child's 
> subprogram that will be called.  (The dispatching will look at the 
> actual tag, not at the designated type.)  And as I said, don't do that. 
>  It can be made to work, but in general it is not what you want, and the 
> extra work at compile time (or during debugging) to resolve ABE (access 
> before elaboration) problems just isn't worth it.

Yes, exactly! This is what I have been getting at all along. And what I've
also been saying is that C++ enforces the "don't do that" by dispatching to
the parent type instead of to the child type in constructors. It does that
by dynamically altering the tag (in Ada terms) of the object during the
construction and destruction process. (C++ is in a more complex situation
than Ada here becuase of multiple and virtual inheritance cases.) But in
doing so, it rubs DK the wrong way, because his philosophy requires objects
to never change their type dynamically.

> Oh, they'll get ya.  The point I keep trying to make is that only 
> language lawyers and compiler vendors should worry about those cases.

Sure, but who else hangs out on c.l.a.? :-)