Re: Sinkability considered harmful

["Gustavo J. A. M. Carneiro" <gjc inescporto pt>]

On Tue, 2006-01-03 at 19:22 -0500, Owen Taylor wrote:
> On Wed, 2006-01-04 at 00:15 +0000, Gustavo J. A. M. Carneiro wrote:
> > On Tue, 2006-01-03 at 18:52 -0500, Owen Taylor wrote:
> > > On Tue, 2006-01-03 at 23:43 +0000, Gustavo J. A. M. Carneiro wrote:
> > > >   Completely agree.  Interesting read too.   I'd just like to add one
> > > > more thing.
> > > > 
> > > >   g_object_new *should* always return a new reference, to be owned by
> > > > the caller.  It usually does, except for g_object_new(GTK_TYPE_WINDOW,
> > > > NULL), in which case the caller does not own the object ref.  I don't
> > > > quite understand how this happened.  It should not be due to backward
> > > > compatibility because this is a new API (in glib 2.0). 
> > > 
> > > See my last mail explaining why g_object_new(GTK_TYPE_WINDOW) is just
> > > like g_object_new(GTK_TYPE_ENTRY). You don't own the initial reference
> > > in either case.
> > > 
> > 
> >   In your last email you don't say anything about GTK_TYPE_ENTRY, as far
> > as I can see. 
> 
> Just an example of the behavior that occurs for EVERY TYPE OF WIDGET.
> 
> >  And the explanation  "GtkWindow's are created owning
> > their own refcount, which they unref on ::destroy"  does not justify
> > anything, it merely states a fact.  I can almost understand why, in C,
> > gtk_window_new() can return a borrowed reference.  But g_object_new() is
> > a rather different API; it is mostly oriented towards language bindings
> > (or at least that's what it looks to me) and so it should be clean of
> > the inconsitencies that plague the gtk_*_new functions.
> > 
> >   And are you sure g_object_new(GTK_TYPE_ENTRY) returns a borrowed
> > reference?  If so, you may have uncovered a PyGTK bug, and would just
> > emphasizes how bad this inconsistency is.
> 
> Whenever you create a descendant of GtkObject with g_object_new(), you
> get an object with an ephemeral reference count.
> 
>  - For most GtkObjects, the reference is owned by *nobody* (definitely
>    not by you)
>  - For GtkWindow descendants, the reference is owned by GTK+ and will
>    be released on destroy().
> 
> In either case, the sequence
> 
>  g_object_ref(object);
>  gtk_object_sink(object);
> 
> Gives you a refcount that you own. This is mandatory if you are going
> to hold onto a pointer to the object and I'm pretty positive that
> PyGTK in fact does this.

  Oh, that.  I thought you were implying that GTK_TYPE_ENTRY was somehow
a special case.  Now I see you mean it's like all GtkObject's.  That is
handled in pygtk indeed.  But a bug existed in pygtk for a month or so
due to this issue.  Luckily someone (not me) spotted it early...

  Regards,

-- 
Gustavo J. A. M. Carneiro
<gjc inescporto pt> <gustavo users sourceforge net>
The universe is always one step beyond logic