[boost] Re: destructor in linked_ptr_base

From: Gavin Collings (gcollings_at_[hidden])
Date: 2000-03-21 12:13:30

"borgerding, mark a." <marka-_at_[hidden]> wrote: 
original article:http://www.egroups.com/group/boost/?start=2709
> 
> There are a few reasons I shied away from using template friends
> 1) Compiler support for template friends is less than universal.
Avoiding
> them reduces the amount of #ifdef code to maintain.
> 2) I don't like using friends unless they clearly strengthen
encapulation
> (This point is arguable for linked_ptr_base)
> 3) I think it reads better without the template friends. (Personal
> preference perhaps)

There do seem to be arguments in both directions for this type of
thing.  I tend to go with Scott Meyers et al and use public inheritance
only to express an is-a relationship.  Though I have to confess to
getting a little tired of the using directives that the approach
implies (and have bypassed them on occasion).

Answering your points.

1) Yes it is a pain that template friends aren't universally supported,
but hopefully, it's a temporary situation.

2) The argument for increased encapsulation is exactly that for which
Miki proposed his fix - that of clients getting hold of a
linked_ptr_base pointer.  This is highly unlikely in itself, since
linked_ptrs would typically be used by value, so polymorphism wouldn't
enter in to it.  But having acknowledged that a problem exists, better
to make more explicit the fact that a linked_ptr should not be used as
a linked_ptr_base IMO.

3) My personal preference leans the other way.  Not strongly though, if
you say no, I'll leave it as it is.

Gavin