Re: [Chicken-users] non-finalized object in SWIG

[Daishi Kato]

Hi,

Although my question was not that clear,
you gave me the right answer:
The helper function would certainly solve it.
Thanks for your suggestion.

There is another weird issue with SWIG,
which I'm not sure if I can describe it clearly.
It would be much easier if you could access
to the SVN repo and try the wxchicken egg.

Daishi

At Tue, 06 Jun 2006 09:15:13 -0500,
John Lenz wrote:
> 
> Daishi Kato wrote:
> > To SWIG experts,
> > 
> > My question is if it is possible to create
> > an object that is not garbage collected.
> > DISOWN can be specified to input typemaps,
> > but can an object that is created by a constructor
> > be DISOWNed?
> 
> Yes, if you pass an object that was originally created by a constructor
> (and is marked for garbage collection), the DISOWN typemap will remove
> it from the garbage collector.  The typemap basically just calls
> C_do_unregister_finalizer(s)
> 
> > 
> > I would like to have sort of output typemaps with DISOWN.
> > 
> > Note that I'm not yet used to SWIG, but it looks pretty nice.
> > Daishi
> > 
> >
> 
> Perhaps the easiest way would be to create a helper function:  something
> like
> 
> %inline %{
> Foo *makeFoo(...) {
>   return new Foo(...);
> }
> %}
> 
> SWIG assumes by default that pointers that are returned from functions
> are not added for garbage collection.  You have to specifically add a
> %newobject tag to functions when you want the return value to be
> collected.  (Note that from SWIGs point of view, a constructor is just
> another function, except that SWIG automatically adds the %newobject tag
> to constructors)
> 
> You could play some games with the definition of this function on the
> chicken/scheme side too, so the helper looks like the real constructor.
> (define old-new-Foo new-Foo) (set! new-Foo makeFoo)
> 
> John
>