Re: [libxml++] Re: [Libxmlplusplus-general] Node ownership

[Stefan Seefeld <seefeld sympatico ca>]

Murray Cumming wrote:

> > 1) you suggest an additional member: 'owned_by_libxml', which isn't
> >    necessary as you can determine by inspecting the _impl whether it
> >    is linked into a tree.
>
>
> Yes, that might work, but I'd prefer not to access libxml's private
> structures.

what is a private structure ? I agree that we have to be very cautious
to only use things part of the public API. I probably should ask DV
which members of the various structs he considers public and which not.

> > 2) you need an accessible destructor, so you can delete the node
> >    explicitely, after having checked that you are allowed to
> >
> >    if (!node->is_owned_by_libxml()) delete node;
> >
> >    or equivalent. That doesn't look very nice.
>
>
> Or just assume that you know what you are doing. The existence of an
> is_owned_by_libxml() method wouldn't force you to use it.

Yes, but even then I'd prefer to be able to just throw
'invalid_argument' or something, instead of watching the application
crash.

But being able to use the delete operator would be very hacky, because
it implies a circular dependency that you'd need to break out explicitely:

Node::~Node()
{
  if (_impl)
  {
    _impl->private = 0; // make sure this destructor isn't called twice
    xmlFreeNode(_impl);
  }
}

Stefan