Re: controlled initialization

[mheaney@on2.com (Matthew Heaney)]

Hyman Rosen <hyrosen@mail.com> wrote in message news:<1040049195.294541@master.nyc.kbcfp.com>...
> 
> Ooh, ooh, I know, I know! I remember this from a thread
> a while ago. Init isn't called for objects that are
> initialized by aggregates. A rationale is that since
> you are supplying all the fields in the aggregate, you
> can just do whatever setup the Init proccedure would
> have done.

The real problem is when you're declaring a deferred constant, e.g.

package P is

   type T is private;

   O : constant T;

private

   type T is new Controlled with null record;

   procedure Initialize (O : in out T);

   O : constant T := (Controlled with null record);

end P;

The problem is that the body of P hasn't elaborated at the moment when
object O is elaborated.  Were Initialize to be called at the point of
elaboration of O, then Program_Error would be raised because the body
of Initialize hasn't been elaborated yet.

So for aggregate initialization, Initialize doesn't get called, and
all initialization is done in-place.