ffc team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

On 26 April 2011 17:08, Johan Hake <johan.hake@xxxxxxxxx> wrote:

> On Tuesday April 26 2011 01:01:55 Martin Sandve Alnæs wrote:
> > I'm not sure if this is safe or even solves anything.
> > If there are circular references a.b = b; b.a = a,
> > a.__del__ won't be called if the reference from
> > b.a is still intact, since a.__del__ is called when
> > the reference count of a goes to 0. Adding the
> > __del__ function will also stop the cyclic reference
> > detection in Python from cleaning up. That is my
> > understanding after reading
> > http://docs.python.org/reference/datamodel.html
> > just now. Correct me if I'm wrong!
>
> If the above situation was correct you would be right. As it is now a
> preprocessed form keeps a reference to form_data and form_data keeps a
> reference to the preprocessed form => Ciruclar dependency.
>

I.e. a.b = b; b.a = a.

I tried to break that by deleting the preprocessed form from its form_data,
> when the original form is deleted (not the preprocessed one.) When this
> happens the preprocessed form will be deleted (I guess).
>

A guess is not enough :)

I don't feel confident about the __del__ patch.
As you say, removing the circular references sounds like a better solution.

Martin