python: ../Objects/capsule.c:321: capsule_traverse: Assertion `capsule->traverse_func != NULL' failed.

$python3.13 -m venv venv_313$source venv_313/bin/activate$pip install matplotlib==3.9.2$python -X dev test.py

importgcfromcollectionsimportdequefrommatplotlib.figureimportFigurefrommatplotlib.linesimportLine2Dfrommatplotlib.collectionsimportPathCollectiondefget_children(parent):ifparent.__class__.__qualname__=="PyCapsule":print(f"About to call gc.get_referents on{repr(parent)}")children=gc.get_referents(parent)# gc.get_referrers does not segfault, but gc.get_referents doesifparent.__class__.__qualname__=="PyCapsule":print(f"There are{len(children)} children")returnchildrendefbreadth_first_search(start):to_visit=deque([start])explored=set()try:gc.disable()# Can repro without this, but it should make behavior more consistentwhilelen(to_visit)>0:parent=to_visit.popleft()forchildinget_children(parent):ifid(child)inexplored:continueexplored.add(id(child))to_visit.append(child)finally:gc.enable()deffind_reference_cycles():fig=Figure()ax=fig.add_subplot()ax.plot([1])fig.clear()breadth_first_search(fig)if__name__=="__main__":find_reference_cycles()

$python -VVPython 3.13.0rc2 (main, Sep  9 2024, 22:55:42) [GCC 11.4.0]$python -X dev test.pyAbout to call gc.get_referents on <capsule object "pybind11_function_record_capsule" at 0x7f79954f34d0>Fatal Python error: Segmentation faultCurrent thread 0x00007f79e687f280 (most recent call first):  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 10 in get_children  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 22 in breadth_first_search  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 35 in find_reference_cycles  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 38 in <module>Extension modules: numpy._core._multiarray_umath, numpy.linalg._umath_linalg, PIL._imaging, kiwisolver._cext (total: 4)Segmentation fault (core dumped)

$python -VVPython 3.13.0rc2 (main, Sep  9 2024, 22:55:42) [GCC 11.4.0]$python -X dev test.pyAbout to call gc.get_referents on <capsule object "pybind11_function_record_capsule" at 0x7f0c31adba80>python: ../Objects/capsule.c:321: capsule_traverse: Assertion `capsule->traverse_func != NULL' failed.Fatal Python error: AbortedCurrent thread 0x00007f0c82d1a280 (most recent call first):  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 10 in get_children  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 22 in breadth_first_search  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 35 in find_reference_cycles  File "/home/justin/tmp/matplotlib_py313_segfault/test.py", line 38 in <module>Extension modules: numpy._core._multiarray_umath, numpy.linalg._umath_linalg, PIL._imaging, kiwisolver._cext (total: 4)Aborted (core dumped)

$python -VVPython 3.12.6 (main, Sep 10 2024, 00:05:17) [GCC 11.4.0]$python -X dev test.pyAbout to call gc.get_referents on <capsule object "pybind11_function_record_capsule" at 0x7f85a852a570>There are 0 children[ ... many similar log lines removed ... ]