[Python-Dev] C new-style classes and GC

[Jeremy Hylton]

On Fri, 2003-05-16 at 13:08, Jim Fulton wrote:
> If you write types the New Way, there are no PyObject_New calls and
> no need to call PyObject_GC_Track.

I don't follow.  There are plenty of types that are garbage collectable
that also use PyObject_GC_New.  One example is PyDict_New().  If
something is widespread in the Python source tree (a common source of
example code for programmers), it ought to be documented.

> > It's not clear to me what the one right way to implement a tp_dealloc
> > slot is.  I've seen two common patterns in the Python source: call
> > obj->ob_type->tp_free or call PyObject_GC_Del.  The type object
> > initializes tp_free to PyObject_GC_Del, so in most cases the two
> > spellings are equivalent.  Calling PyObject_GC_Del feels more
> > straightforward to me.
> 
> You need to call obj->ob_type->tp_free to support subclassing.
> 
> I suggest that every new type should call obj->ob_type->tp_free
> as a matter of course.

If the type is going to support subclassing.

Jeremy