RE: generic refcounted object perl binding

Even if we have to bless the referenCE, does the blessing actually bind package subs on the referenT?

I'm trying to make a ref-counted C++ class using an HV's refcnt. Thus when the HV's refcount drop to zero, it should also delete the binded C++ object. It seems I should create an SV reference for my HV, and bless that SV.

However, what should I do if I don't want to have a SV reference?

> Date: Wed, 26 Oct 2011 10:20:11 +0200
> From: kaffeetisch gmx de
> To: gtk-perl-list gnome org
> Subject: Re: generic refcounted object perl binding
> On 26.10.2011 07:49, YangXi wrote:
> > Ano ther question about wrapper design, in function gperl_new_object()
> > where an new wrapper is newly created:
> >
> > ......
> > obj = (SV *)g_object_get_qdata (object, wrapper_quark);
> >
> > if (!obj) {
> > ......
> > // created a hash
> > obj = (SV *)newHV () ;
> > _gperl_attach_mg (obj, object);
> > g_object_ref (object);
> >
> > // created a SV wrapper for the hash
> > sv = newRV_noinc (obj);
> > sv_bless (sv, stash);
> > ......
> > }
> > ......
> >
> > Why don't bless the HV directly, but instead creating another SV
> > wrapping the HV, and bless that SV instead?
> That is how references work at the perl C API level, but also kind of
> how they work in Perl directly. A reference to something is a separate
> SV (with its own refcount, etc.), just like in Perl, where you can take
> multiple references to the same variable. And if you to put something
> into some namespace, you have to bless the reference, not the referent.
> > Why use noinc to create the wrapper? Shouldn't the SV wrapper holding a
> > reference for HV?
> This is a common pattern when constructing references: we use
> newRV_noinc as opposed to newRV because 'obj' from above is a new HV and
> we want 'sv' to take ownership of the initial refcount. Thus, when 'sv'
> goes out of scope it would normally take 'obj' with it. In Glib::Object
> this is a bit more complicated because we want 'obj' to survive so that
> we can find it later and hand it out again. This is done by
> incrementing its refcount in Glib::Object::DESTROY (which is called when
> 'sv' goes out of scope).
> I wanted to link to some XS tutorial covering all this, but the examp le
> at <> actually uses a
> different pattern to achieve the same thing: it mortalizes both the
> referent and the reference, so when the xsub returns both end up having
> refcount=1 as well. (The sv_2mortal call for the reference is hidden in
> the 'SV*' typemap.)
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