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memory corruption by ndarray_instance.data assignment (data should be made readonly) (Trac #1275) #1873
Description
Original ticket http://projects.scipy.org/numpy/ticket/1275 on 2009-10-25 by trac user mcieslik, assigned to unknown.
It's probably not a bug, but I'd like to ask for clarification. I try to make two arrays share memory. I create big array from small arrays (this involves a copy e.g. by vstack). Create slice/views of the big array corresponding to the small arrays and do a array.data assignment i.e.:
small_array.data = big_array[some_slice].data
This works, both arrays can now modify the same memory, but is not safe as it can lead to memory corruption (see below). My first question: is this considered very very bad practice and if so how to point an ndarray instance to a new memory safely.
In [1]: import numpy as np
In [2]: zeros = np.zeros((2,2))
In [3]: double_zeros = np.vstack((zeros, zeros))
In [4]: double_zeros
Out[4]:
array([[ 0., 0.],
[ 0., 0.],
[ 0., 0.],
[ 0., 0.]])
In [5]: zeros.data = double_zeros[0:3].data
In [6]: double_double_zeros = np.vstack((double_zeros,double_zeros))
In [7]: double_double_zeros
Out[7]:
array([[ 0., 0.],
[ 0., 0.],
[ 0., 0.],
[ 0., 0.],
[ 0., 0.],
[ 0., 0.],
[ 0., 0.],
[ 0., 0.]])
In [8]: double_zeros.data = double_double_zeros[0:5].data
In [9]: zeros
Out[9]:
array([[ 1.25794259e-312, 9.42758674e-317],
[ 1.58101007e-322, 2.37151510e-322]])
In [10]: zeros[0][0] = 1.1
In [11]: zeros
Out[11]:
array([[ 9.88131292e-324, 3.95252517e-323],
[ 4.94065646e-324, 2.42092166e-322]])
In [12]: zeros[0][0] = 2
In [13]: *** glibc detected *** /usr/bin/python: corrupted double-linked list: 0x000000000117dab0 ***
(this kills the interpreter)
Activity
thouis commentedon Oct 19, 2012
@rgommers wrote on 2010-07-18
Asking this on the mailing list will probably get you an answer. Here it probably won't any time soon.
thouis commentedon Oct 19, 2012
@mwiebe wrote on 2011-03-25
This looks like a bug to me - data should be a read-only attribute of the array class. This crashes for me in 1.6 beta.
thouis commentedon Oct 19, 2012
Milestone changed to
NumPy 2.0by @mwiebe on 2011-03-25thouis commentedon Oct 19, 2012
Title changed from
memory corruption by ndarray_instance.data assignmenttomemory corruption by ndarray_instance.data assignment (data should be made readonly)by @mwiebe on 2011-03-25charris commentedon Feb 16, 2014
Oh, that is very, very bad ;) And we should not allow it.
BUG: make data attribute of ndarray read-only
jaimefrio commentedon Mar 27, 2016
Fixed by #7275, at least whenever the deprecation is made an actual error.