[New-bugs-announce] [issue35507] multiprocessing: seg fault when creating RawArray from numpy ctypes

[sh37211]

New submission from sh37211 <mcskwayrd at yahoo.com>:

After creating this post on StackOverflow...
https://stackoverflow.com/questions/53757856/segmentation-fault-when-creating-multiprocessing-array
...it was suggested by one of the respondents that I file a bug report.


The following code produces segmentation faults on certain OSes (Linux: Ubuntu 16.04, 18.04 and Debian) but not others (Mac 10.13.4):

    import numpy as np
    from multiprocessing import sharedctypes

    a = np.ctypeslib.as_ctypes(np.zeros((224,224,3)))
    b = sharedctypes.RawArray(a._type_, a)

The segmentation fault occurs upon the creation of the multiprocessing.sharedctypes.RawArray. 

As a workaround, one can declare an intermediate variable, e.g. "a2", and write

    a = np.zeros((224,224,3))
    a2 = np.ctypeslib.as_ctypes(a)
    b = sharedctypes.RawArray(a2._type_, a2)

User kabanus seemed to think it was more likely to be an error with multiprocessing than with numpy. 

Using Anaconda python distribution, Python 3.5 and 3.6.  Have not tried 3.7 or 3.8 yet.

----------
components: Library (Lib), ctypes
messages: 331888
nosy: sh37211
priority: normal
severity: normal
status: open
title: multiprocessing: seg fault when creating RawArray from numpy ctypes
type: crash
versions: Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35507>
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