Re: "Inefficiency" of controlled types

["David S. Gibson" <dgibson@cis.ohio-state.edu>]

Matthew Heaney wrote:
> 
> I'm curious about early in a derivation tree controlled types should be
> introduced, given that there is some overhead in their use.

  . . . 
  
> However, we really only need this for unbounded forms, which use heap
> allocation.  For bounded forms (implemented as an array), finalization is
> not really required, and so there is an "unnecessary" amount of overhead.
> 
> We don't have to introduce Controlled that early in the hierarchy.  Clients
> that need it could declare a Controlled wrapper for that stack component
> that requires finalization (say, a list component used to implement the
> unbouned stack).

When I was using controlled types for the same purpose, I found that I
had to
derive generic components from Ada.Finialization.Limited_Controlled at
the
root level due to the accessibility rules of Ada.  If I recall
correctly, an 
instance of a generic controlled type package needs to be declared as a 
library-level package.  While I put the derivation from
Limited_Controlled in
the private part, I would have liked to move it down some in the
hierarchy.

Dave
--
dgibson@cis.ohio-state.edu