On 7/15/10 12:43 PM, Stefan Behnel wrote:
> Hi, note that this is a question for the cython-users mailing list.

Sorry. Since I am also questioning the implementation, this seemed like a 
reasonable place. :-)

> Robert Kern, 15.07.2010 19:38:
>> What are the recommendations for the use of the "object" type versus 
>> "PyObject
>> *"? Ondrej pointed out a potential bug in my line_profiler package:
>>
>> http://github.com/certik/line_profiler/commit/dc3ad198f8a810d34da5da71ffccf01c5e05a161
>>
>> I have a cdef function that serves as the callback for the PyEval_SetTrace()
>> functionality. It has a PyObject* argument that is sometimes NULL. This 
>> argument
>> happens to be unused. In the version of Cython I originally developed
>> line_profile under , no code referenced this argument. In the development
>> version of Cython that Ondrej used to compile line_profiler, a Py_INCREF is
>> apparently generated. When the argument is NULL, this obviously fails.
>>
>> Is this intentional? Should "object" be avoided when the argument could 
>> possibly
>> be NULL? Or should the generated code use Py_XINCREF/Py_XDECREF instead to 
>> avoid
>> failure?
>
> In Cython, object and PyObject* are not compatible. The first is an
> automatically ref-counted object, whereas the second is a plain pointer.
> For an argument that can be NULL, you cannot use object.

Would using Py_XINCREF/Py_XDECREF allow the automatic refcounting to simply 
ignore NULL pointers but still work for the usual case? Or would there be other 
issues?

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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