#30274: Segfault on iteration of GEOS Polygons/LinearRings
-------------------------------------+-------------------------------------
Reporter: Murray | Owner: nobody
Christopherson |
Type: Bug | Status: new
Component: GIS | Version: 2.1
Severity: Normal | Keywords: geos gis
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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**Environment Details**
Ubuntu 14.04 (trusty)
Python 3.6.8 (via package manager, unofficial repo: ppa:deadsnakes/ppa)
Django 2.1.7 (via pip)
libgeos (both 3.4.2 via apt-get, and 3.7.1 via source distribution)
First and foremost, I am aware that the OS is a bit older (hence the
unofficial installation routes of some newer dependencies), but I was
unable to find any reason these components shouldn't play nice.
**Steps to reproduce**
I have a minimal script showcasing the issue:
{{{
from django.contrib.gis.geos import Polygon
def main():
polygon = Polygon( ((0.0, 0.0), (0.0, 50.0), (50.0, 50.0), (50.0,
0.0), (0.0, 0.0)) )
for p in polygon[0]:
print('Longitude:', p[0])
print('Latitude:', p[1])
if __name__ == '__main__':
main()
}}}
**Expected Behaviour**
Output to stdout, something like:
{{{
Latitude: 0.0
Longitude: 0.0
Latitude: 0.0
Longitude: 50.0
...
}}}
**Observed Behaviour**
Output to stderr:
{{{
Segmentation fault (core dumped)
}}}
**Notes**
It should be noted, when originally observed, there was a stacktrace
(which I won't post in full, as it's mostly uWSGI functions), but the
relevant section suggested the segfault is in `GEOSCoordSeq_getSize` in
`libgeos.so`, which leads me to believe the issue may be in
https://github.com/django/django/blob/master/django/contrib/gis/geos/prototypes/coordseq.py.
Furthermore, this issue was uncovered during a Python 2 to 3 migration
attempt. The issue did not manifest in this environment:
Ubuntu 14.04 (trusty)
Python 2.7.12 (via package manager, unofficial repo: ppa:deadsnakes/ppa)
Django 1.11.18 (via pip)
libgeos 3.4.2 (via apt-get)
Lastly, I was able to find a workaround (in case anyone else encounters
this). This un-Pythonic variation seems to work:
{{{
from django.contrib.gis.geos import Polygon
def main():
polygon = Polygon( ((0.0, 0.0), (0.0, 50.0), (50.0, 50.0), (50.0,
0.0), (0.0, 0.0)) )
for i in range(len(polygon[0])):
p = polygon[0][i]
print('Longitude:', p[0])
print('Latitude:', p[1])
if __name__ == '__main__':
main()
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/30274>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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