I should mention, that these PyObject_Generic* functions are being used from with __getattribute__, __setattr__, and __delattr__ methods. I should have added that context in the begining.
On Sun, Feb 13, 2011 at 3:37 PM, Chris Colbert <sccolb...@gmail.com> wrote: > The problem with delattr (and thus PyObject_DelAttr) arises when you define > a __delattr__ method on your class. There is not easy way to then call back > into the "normal" python delattr semantics, except by doing > object.__delattr__ (which is not optimized by Cython). > > Futher, calling PyObject_GenericSetattr(obj, name, NULL) appears to be the > proper use, given that it properly follows the descriptor chain and will > call __delete__ if obj.name is a descriptor. > > I would argue that there should be at least some way to pass a NULL pointer > in Cython where a PyObject* is expected. > > > On Sun, Feb 13, 2011 at 3:31 PM, Greg Ewing > <greg.ew...@canterbury.ac.nz>wrote: > >> Chris Colbert wrote: >> >>> I have cython file which is using PyObject_GenericSetAttr >>> Now in my script I am using that function to generically delete an >>> attribute by passing a NULL as the last value (this is proper way to trigger >>> a generic delattr in the Python c-api) >>> >> >> I would have thought the proper way to do that was to use >> PyObject_DelAttr, which Pyrex exposes as delattr(). >> >> I don't think PyObject_GenericSetAttr is even meant to be >> called directly -- it's intended for filling the tp_setattr >> slot of type objects. >> >> >> This causes a segfault because the NULL is getting increfed via Py_INCREF >>> instead of Py_XINCREF. >>> >> >> I would recommend against trying to "fix" this. You got >> away with it before because you happened to be passing the >> NULL value directly to a function which is expecting it. >> But casting NULL to an object reference is not something >> that should be encouraged, because in any other context it >> would quickly lead to disaster. >> >> -- >> Greg >> > >
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