cdef'd list raises wrong exception on append when list is None

[hoytak]

Hello,

In cython-devel version 1497, I think a check for None is not being inserted for list.append(). The following code

def crash():
    cdef list l = None

    l.append(2)

raise the following exception:

In [4]: list_as_none.crash()
---------------------------------------------------------------------------
SystemError                               Traceback (most recent call last)

/home/hoytak/workspace/cython-tests/list_as_none/<ipython console> in <module>()

/home/hoytak/workspace/cython-tests/list_as_none/list_as_none.so in list_as_none.crash (list_as_none.c:219)()
      1 def crash():
      2     cdef list l = None
      3
----> 4     l.append(2)

SystemError: Objects/listobject.c:255: bad argument to internal function

I believe this should be something indicating that l is None.

[scoder]

I guess this is a general problem with the "builtin-type argument to C-API function" mapping. We always need an additional None check when we optimise this.

[robertwb]

OTOH, is this any different than calling a cdef method on a extension class variable containing None?

[scoder]

Yes, because you are not calling a cdef method. You would normally expect a TypeError?, not a SystemError? for this. The reason why you get a SystemError? is an implementation detail of Cython.

This should be fixed in the Optimize.OptimizeBuiltinCalls? transform (currently in cython-unstable), therefore moving it to 0.12.

[scoder]

Runtime None check implemented here:

 http://hg.cython.org/cython-unstable/rev/4495287d2fdb