On 05/12/2012 08:44 PM, Nathaniel Smith wrote:
On Fri, May 11, 2012 at 2:25 PM, Dag Sverre Seljebotn
<d.s.seljeb...@astro.uio.no> wrote:
This comes from a refactor of the work on CEP 1000: A PEP proposal, with a
hack for use in current Python versions and in the case of PEP rejection,
that allows 3rd party libraries to agree on extensions to PyTypeObject.
http://wiki.cython.org/enhancements/cep1001
If this makes it as a PEP, I don't think we need to think about having CEP
1000 accepted as a PEP.
Comments?
There should probably be some discussion of memory management for the
tpe_data pointers. (I assume it's "guaranteed to be valid for as long
as the associated PyTypeObject, and the PyTypeObject is responsible
for making sure any necessary cleanup happens if it gets deallocated",
but a note to this effect would be good.)
What happens if I want to inherit from PyTypeObject (a "metaclass")
and also implement this interface? It is possible? What if I want to
inherit from an existing subclass of PyTypeObject and add on this
interface? I don't know enough gnarly details about how new style
classes are implemented to tell. Would it make sense to make this
memory-layout-equivalent to a PyTypeObject subclass with extra fields?
Hmm. You know what -- this whole thing could probably be a metaclass.
Except I think a PyObject_TypeCheck on the type would be a bit more
expensive than just checking a flag. I think I like having a flag better...
The point of supporting objects with a metaclass is a good one. I don't
know enough details either. I wonder if ob_size field could save us;
basically access extra information at offset
(ob_size != 0) ? ob_size : sizeof(PyTypeObject);
I think that also flags that the type object is allocated on heap? But
at least it allows a way out of you want to use a metaclass (allocate it
on the heap; or perhaps give it a very high refcount).
But I didn't check this in detail yet.
Dag
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