[Python-Dev] Possible bug in complexobject.c (still in Python 2.5)

[Guido van Rossum]

I wouldn't be surprised if this is a genuine bug; the complex type
doesn't get a lot of love from core developers.

Could you come up with a proposed fix, and a unit test showing that it
works (and that the old version doesn't)? (Maybe a good unit test
would require writing a custome C extension; in that case just show
some sample code.)

--Guido

On 5/31/06, Travis E. Oliphant <oliphant.travis at ieee.org> wrote:
>
> I'm curious about the difference between
>
> float_subtype_new  in floatobject.c
> complex_subtype_from_c_complex in complexobject.c
>
> The former uses type->tp_alloc(type, 0) to create memory for the object
> while the latter uses PyType_GenericAlloc(type, 0) to create memory for
> the sub-type (thereby by-passing the sub-type's own memory allocator).
>
> It seems like this is a bug.   Shouldn't type->tp_alloc(type, 0) also be
> used in the case of allocating complex subtypes?
>
> This is causing problems in NumPy because we have a complex type that is
> a sub-type of the Python complex scalar.  It sometimes uses the
> complex_new code to generate instances (so that the __new__ interface is
> the same),  but because complex_subtype_from_c_complex is using
> PyType_GenericAlloc this is causing errors.
>
> I can work around this by not calling the __new__ method for the base
> type but this is not consistent.
>
>
> Thanks for any feedback,
>
> -Travis
>
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-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)