[pypy-dev] Bringing Cython and PyPy closer together

[Stefan Behnel]

Stefan Behnel, 26.02.2012 20:54:
> Amaury Forgeot d'Arc, 18.02.2012 15:41:
>> 2012/2/18 Stefan Behnel
>>> Here's an example.
>>>
>>> Python code:
>>>
>>>  def print_excinfo():
>>>      print(sys.exc_info())
>>>
>>> Cython code:
>>>
>>>  from stuff import print_excinfo
>>>
>>>  try:
>>>      raise TypeError
>>>  except TypeError:
>>>      print_excinfo()
>>>
>>> With the code removed, Cython will not store the TypeError in
>>> sys.exc_info(), so the Python code cannot see it. This may seem like an
>>> unimportant use case (who uses sys.exc_info() anyway, right?), but this
>>> becomes very visible when the code that uses sys.exc_info() is not user
>>> code but CPython itself, e.g. when raising another exception or when
>>> inspecting frames. Things grow really bad here, especially in Python 3.
>>
>> I think I understand now, thanks for your example.
>> Things are a bit simpler in PyPy because these exceptions are
>> stored in the frame that is currently handling it. At least better than
>> CPython
>> which stores it in one place, and has to somehow save the state of the
>> previous frames.
>> Did you consider adding such a function to CPython?
>> "PyErr_SetCurrentFrameExceptionInfo"?
>>
>> For the record, pypy could implement it as:
>> space.getexecutioncontext().gettopframe_nohidden().last_exception =
>> operationerr
>> i.e. the thing returned by sys.exc_info().
> 
> I've dropped a patch for CPython in the corresponding tracker ticket:
> 
> http://bugs.python.org/issue14098
> 
> The (trivial) implementation of the two functions is at the end of this file:
> 
> http://bugs.python.org/file24613/exc_info_capi.patch
> 
> Could you add them to PyPy?

Anyone?

Stefan