"""

Check that Cython generates a tp_clear function that actually clears object

references to NULL instead of None.

Discussed here: http://article.gmane.org/gmane.comp.python.cython.devel/14833

"""

from cpython.ref cimport PyObject, Py_TYPE

cdef class ExtensionType:

    """

    Just a type which is handled by a specific C type (instead of PyObject)

    to check that tp_clear works when the C pointer is of a type different

    from PyObject *.

    """

# Pull tp_clear for PyTypeObject as I did not find another way to access it

# from Cython code.

cdef extern from "Python.h":

    ctypedef struct PyTypeObject:

        void (*tp_clear)(object)

cdef class TpClearFixture:

    """

    An extension type that has a tp_clear method generated to test that it

    actually clears the references to NULL.

    >>> fixture = TpClearFixture()

    >>> isinstance(fixture.extension_type, ExtensionType)

    True

    >>> isinstance(fixture.any_object, str)

    True

    >>> fixture.call_tp_clear()

    >>> fixture.check_any_object_status()

    'NULL'

    >>> fixture.check_extension_type_status()

    'NULL'

    """

    cdef readonly object any_object

    cdef readonly ExtensionType extension_type

    def __cinit__(self):

        self.any_object = "Hello World"

        self.extension_type = ExtensionType()

    def call_tp_clear(self):

        cdef PyTypeObject *pto = Py_TYPE(self)

        pto.tp_clear(self)

    def check_any_object_status(self):

        if <void*>(self.any_object) == NULL:

            return 'NULL'

        elif self.any_object is None:

            return 'None' 

        else:

            return 'not cleared'

    def check_extension_type_status(self):

        if <void*>(self.any_object) == NULL:

            return 'NULL'

        elif self.any_object is None:

            return 'None' 

        else:

            return 'not cleared'