I tend to use ndarray.copy() in python code -- no reason you couldn't do the same in Cython. If you want to take any array-like object that may not have a copy() method, you could call asanyarray() first: -CHB On Sat, Nov 12, 2016 at 9:00 AM, Pavlyk, Oleksandr < oleksandr.pavlyk@intel.com> wrote:

Hi,

In my Cython code a function processes it argument x as follows:

x_arr = PyArray_CheckFromAny(

x, NULL, 0, 0,

cnp.NPY_ELEMENTSTRIDES | cnp.NPY_ENSUREARRAY | cnp.NPY_NOTSWAPPED, NULL)

if x_arr is not x:

in_place = 1 # a copy was made, so we can work in place.

The logic is of the last line turns out to be incorrect, because the input x can be a class with an array interface:

class FakeArray(object):

def __init__(self, data):

self._data = data

self.__array_interface__ = data.__array_interface__

Feeding my function FakeArray(xx), x_arr will point into the content of xx, resulting in unwarranted content overwrite of xx.

I am trying to replace that condition with

if x_arr is not x and cnp.PyArray_Check(x):

# a copy was made, so we can work in place.

in_place = 1 if cnp.PyArray_CHKFLAGS(x_arr, cnp.NPY_WRITEABLE) else 0

I am wondering if I perhaps overlooked some case.

Thank you,

Sasha

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-- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov

I tend to use ndarray.copy() in python code -- no reason you couldn't do the same in Cython. If you want to take any array-like object that may not have a copy() method, you could call asanyarray() first: -CHB On Sat, Nov 12, 2016 at 9:00 AM, Pavlyk, Oleksandr < oleksandr.pavlyk@intel.com> wrote:

Hi,

In my Cython code a function processes it argument x as follows:

x_arr = PyArray_CheckFromAny(

x, NULL, 0, 0,

cnp.NPY_ELEMENTSTRIDES | cnp.NPY_ENSUREARRAY | cnp.NPY_NOTSWAPPED, NULL)

if x_arr is not x:

in_place = 1 # a copy was made, so we can work in place.

The logic is of the last line turns out to be incorrect, because the input x can be a class with an array interface:

class FakeArray(object):

def __init__(self, data):

self._data = data

self.__array_interface__ = data.__array_interface__

Feeding my function FakeArray(xx), x_arr will point into the content of xx, resulting in unwarranted content overwrite of xx.

I am trying to replace that condition with

if x_arr is not x and cnp.PyArray_Check(x):

# a copy was made, so we can work in place.

in_place = 1 if cnp.PyArray_CHKFLAGS(x_arr, cnp.NPY_WRITEABLE) else 0

I am wondering if I perhaps overlooked some case.

Thank you,

Sasha

_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org https://mail.scipy.org/mailman/listinfo/numpy-discussion

-- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov