[Python-modules-team] Bug#750362: python-graph: FTBFS - recursion causing excessive stack usage

[Michael Tautschnig]

Package: python-graph
Version: 1.8.2-4
Usertags: goto-cc

During a rebuild of all Debian packages in a clean sid chroot (using cowbuilder
and pbuilder) the build failed with the following error.

[...]
test_topological_sort_on_very_deep_graph (unittests-sorting.test_topological_sorting) ... Segmentation fault
Makefile:69: recipe for target 'test' failed
make[2]: *** [test] Error 139
make[2]: Leaving directory '/srv/jenkins-slave/workspace/sid-goto-cc-python-graph/python-graph-1.8.2'
debian/rules:20: recipe for target 'override_dh_auto_test' failed
make[1]: *** [override_dh_auto_test] Error 2

(The full build log is attached.) Upon inspection via gdb it becomes apparent
that this is caused by excessive recursion, which eventually causes a stack
overflow. This is due to the following lines:

http://sources.debian.net/src/python-graph/1.8.2-4/tests/unittests-sorting.py?hl=82,83#L82

Changing the numbers to 16876 and 16875, respectively, was the maximum I got to
work.

I'm leaving the severity untouched as (a) this is a test case only and (b)
really the underlying code should be reconsidered to turn recursion into a loop
- after all the present number of nodes doesn't seem terribly large.

Best,
Michael

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