[rox-devel] Re: ROX-Lib2 broken: Got it!

[Guido S. <__g...@we...>]

On Mon, 30 May 2005 20:30:44 +0100
Stephen Watson <st...@ke...> wrote:

> "Ken Hayber" <ke...@ha...> wrote:
> 
> > On Mon, May 30, 2005 9:46 am, Stephen Watson said:
> > > Guido Schimmels <__g...@we...> wrote:
> > >
> > >>
> > >> Those changes break it for me:
> > >>
> > >> 19-May-2005
> > >> ~~~~~~~~~~~
> > >> Clean up of icon theme handling (Stephen Watson).
> > >>
> > >>
> > >> Sympton when trying to open a SaveBox:
> > >>  no SaveBox, 100% CPU ad infinitum
> > >
> > > Running what?
> > >
> > >> 18-May-2005 is OK.
> > >>
> > >> (gtk-2.6.4 pygtk-2.6.2)
> > >
> > > Archive works with gtk 2.4 and pygtk 2.4  Any body else with 2.6?
> > 
> > Yup.  No problems here.  gtk 2.6.7, pygtk 2.6.1
> 
> It might be theme related then.

No, I think I got it.
In fact removing info.free() (good catch, Ken!) is the proper fix.
This doesn't come at the expence of a leak, but is perfectly alright.
And this is why:

From the pygtk gtk-doc reference:

<quote>

class gtk.IconInfo(gobject.GBoxed):
....

+-- gobject.GBoxed

Description

gobject.GBoxed is an abstract base class that encapsulates an opaque chunk of data to provide an object-oriented interface and a type that is registered with the GLIB type system. A boxed type is registered with functions that provide for the copying and freeing of the underlying data structure - this allows PyGTK to encapsulate these as Python objects.

</quote>

So gtk.IconInfo registers callbacks with the python interpreter. 
When the object is unreferenced gtk.IconInfo.free() is always implicitly been called.

That fits perfectly with my investigation. I added a gc.collect() after info.free(), then *precisly on function exit* it would segfault.
(Ken found out it's a double-free() - makes sense)

This raises the question why the pygtk devs have implemented gtk.IconInfo.free() in the first place. 
When would you call it - won't it always wreak havoc? 
Probably there is a way to cancel gobject unboxing for a particular object instance?
Anyway, the docs should contain a clear warning.