[Cython] cdef class tp_new should call PyBaseObject_Type.tp_new?

[Stefan Behnel]

Stefan Behnel, 10.01.2014 10:11:
> Simon Jagoe, 09.01.2014 14:04:
>>> Looking at the code in Py3, ISTM that it would be sufficient to do this iff
>>>
>>>         (t->tp_flags & Py_TPFLAGS_IS_ABSTRACT) != 0
>>>
>>> which should be rare enough.
>>>
>>> Obviously requires some user side testing to see if it breaks any other code...
>>
>> Thanks for looking at this. I am wondering if there is a reason why the
>> tp_alloc can't be replaced with the PyBaseObject_Type->tp_new directly?
> 
> I don't know. At least, it's some unnecessary overhead in almost all cases.
> Not sure if that matters, there's enough costly stuff happening at this
> point anyway.
> 
> ISTM that we'd also have to fix the issue that Nils Bruin found, otherwise
> we'd risk even more trouble on user side.
> 
> http://thread.gmane.org/gmane.comp.python.cython.user/10267
> 
> 
>> My understanding is that initially, object's tp_new essentially just
>> called tp_alloc as Cython does now.  Later the abc feature was added
>> with the abstract check happening in object's tp_new, while not changing
>> previous (non-abstract class) behavior.  If Cython were to use this
>> instead of tp_alloc, it would be forward-compatible with future changes
>> to object.
> 
> Agreed.

Let's see what Jenkins has to say about it.

https://github.com/cython/cython/commit/ddaffbe78c06e580ca0d9cd334c7a28a4de5c40b

Stefan