[Python-Dev] C new-style classes and GC (original) (raw)

Jeremy Hylton jeremy@zope.com
16 May 2003 14:12:33 -0400

On Fri, 2003-05-16 at 13:37, Guido van Rossum wrote:

> It's not clear to me what the one right way to implement a tpdealloc > slot is. I've seen two common patterns in the Python source: call > obj->obtype->tpfree or call PyObjectGCDel. The type object > initializes tpfree to PyObjectGCDel, so in most cases the two > spellings are equivalent. Calling PyObjectGCDel feels more > straightforward to me.

But calling tpfree is more correct. This allows a subclass to change the memory allocation policy. (This is also important if a base class is not collectible but a subclass is -- then it's essential that the base class dealloc handler calls tpfree.)

There are dozens of objects in Python that do not call tp_free. For example, range object's have a tp_dealloc that is set to PyObject_Del(). Should we change those? Or should we say that it's okay to call PyObject_Del() and PyObject_GC_Del() from objects that are not intended to be subclassed?

(patch pending :-)

Jeremy