[Bug]: calling pyplot.gca() outside the main thread crashes the interpreter with the MacOS backend #30666
Description
Bug summary
I think #28678 and #28513 are related.
I discovered this while testing matplotlib-venn on the free-threaded build using pytest-run-parallel. I ultimately tracked it down to the plt.gca() call here:
Here is a faulthandler report from me triggering this using the matplotlib-venn test suite. You should be able to trigger it yourself by installing matplotlib-venn from source with pip install -e . then run their test suite with cd tests; pytest --parallel-threads=4 and you'll probably trigger this on a Mac.
Details
Fatal Python error: Aborted
Thread 0x0000000177e5b000 [Thread-8 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1713 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 43 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x0000000176e4f000 [Thread-7 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 86 in _wrapreduction
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 3164 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/transforms.py", line 328 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1968 in get_width_height
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 153 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x0000000175e43000 [Thread-6 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 86 in _wrapreduction
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 3164 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/transforms.py", line 328 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1968 in get_width_height
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 43 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x0000000174e37000 [Thread-5 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 47 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x0000000173e2b000 [Thread-4 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 86 in _wrapreduction
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 3164 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/transforms.py", line 328 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1968 in get_width_height
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 43 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Current thread 0x0000000172e1f000 [Thread-3 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 153 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x0000000171e13000 [Thread-2 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1946 in get_width_height
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 153 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x0000000170e07000 [Thread-1 (closure)] (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 86 in _wrapreduction
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/numpy/_core/fromnumeric.py", line 3164 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/transforms.py", line 328 in max
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1968 in get_width_height
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/backend_macosx.py", line 43 in __init__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 2656 in create_with_canvas
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 1785 in new_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3509 in new_figure_manager_given_figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backend_bases.py", line 3504 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 551 in new_figure_manager
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1041 in figure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 1107 in gcf
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/pyplot.py", line 2784 in gca
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 191 in _render_layout
File "/Users/goldbaum/Documents/matplotlib-venn/matplotlib_venn/_venn2.py", line 173 in venn2
File "<string>", line 2 in <module>
File "/Users/goldbaum/Documents/matplotlib-venn/tests/utils.py", line 94 in exec_ipynb
File "/Users/goldbaum/Documents/matplotlib-venn/tests/functional_test.py", line 18 in test_venn2
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 80 in closure
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1023 in run
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1081 in _bootstrap_inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1043 in _bootstrap
Thread 0x000000020a4860c0 (most recent call first):
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/threading.py", line 1132 in join
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 112 in inner
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/python.py", line 194 in pytest_pyfunc_call
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_callers.py", line 121 in _multicall
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_manager.py", line 120 in _hookexec
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_hooks.py", line 512 in __call__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/python.py", line 1788 in runtest
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 169 in pytest_runtest_call
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_callers.py", line 121 in _multicall
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_manager.py", line 120 in _hookexec
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_hooks.py", line 512 in __call__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 262 in <lambda>
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 341 in from_call
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 261 in call_runtest_hook
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 222 in call_and_report
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 133 in runtestprotocol
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/runner.py", line 114 in pytest_runtest_protocol
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_callers.py", line 121 in _multicall
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_manager.py", line 120 in _hookexec
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_hooks.py", line 512 in __call__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pytest_run_parallel/plugin.py", line 224 in pytest_runtestloop
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_callers.py", line 121 in _multicall
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_manager.py", line 120 in _hookexec
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_hooks.py", line 512 in __call__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/main.py", line 324 in _main
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/main.py", line 270 in wrap_session
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/main.py", line 317 in pytest_cmdline_main
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_callers.py", line 121 in _multicall
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_manager.py", line 120 in _hookexec
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/pluggy/_hooks.py", line 512 in __call__
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/config/__init__.py", line 166 in main
File "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/_pytest/config/__init__.py", line 189 in console_main
File "/Users/goldbaum/.pyenv/versions/3.14.0t/bin/pytest", line 7 in <module>
Current thread's C stack trace (most recent call first):
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _Py_DumpStack+0x44 [0x10099bb50]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at faulthandler_fatal_error+0x240 [0x1009af968]
Binary file "/usr/lib/system/libsystem_platform.dylib", at _sigtramp+0x38 [0x19c52d6a4]
Binary file "/usr/lib/system/libsystem_pthread.dylib", at pthread_kill+0x128 [0x19c4f388c]
Binary file "/usr/lib/system/libsystem_c.dylib", at abort+0x7c [0x19c3fca3c]
Binary file "/usr/lib/libc++abi.dylib", at _ZN10__cxxabiv130__aligned_malloc_with_fallbackEm+0x0 [0x19c4a9384]
Binary file "/usr/lib/libc++abi.dylib", at _ZL28demangling_terminate_handlerv+0x158 [0x19c497cf4]
Binary file "/usr/lib/libobjc.A.dylib", at _ZL15_objc_terminatev+0x9c [0x19c11cdd4]
Binary file "/usr/lib/libc++abi.dylib", at _ZSt11__terminatePFvvE+0x10 [0x19c4a8698]
Binary file "/usr/lib/libc++abi.dylib", at __cxa_get_exception_ptr+0x0 [0x19c4abc30]
Binary file "/usr/lib/libc++abi.dylib", at _ZN10__cxxabiv1L12failed_throwEPNS_15__cxa_exceptionE+0x0 [0x19c4abbd8]
Binary file "/usr/lib/libobjc.A.dylib", at objc_exception_throw+0x1c0 [0x19c112cf8]
Binary file "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation", at _CFBundleGetValueForInfoKey+0x0 [0x19c674154]
Binary file "/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit", at -[NSWindow _initContent:styleMask:backing:defer:contentView:]+0x104 [0x1a05131c8]
Binary file "/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit", at -[NSWindow initWithContentRect:styleMask:backing:defer:]+0x30 [0x1a05130b8]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/_macosx.cpython-314t-darwin.so", at -[Window initWithContentRect:styleMask:backing:defer:withManager:]+0x34 [0x1032cf4a8]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/python3.14t/site-packages/matplotlib/backends/_macosx.cpython-314t-darwin.so", at FigureManager_init+0x144 [0x1032d2480]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at wrap_init+0x14 [0x10085f920]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at wrapperdescr_call+0x180 [0x1007b52ec]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyObject_MakeTpCall+0x13c [0x1007a5464]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyEval_EvalFrameDefault+0x235c [0x1008f7f1c]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyEval_Vector+0x2cc [0x1008f5918]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyObject_VectorcallDictTstate+0xcc [0x1007a52c4]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyObject_Call_Prepend+0x98 [0x1007a64dc]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at call_method+0x7c [0x100857430]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at slot_tp_init+0x2c [0x10085f7f4]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at type_call+0x1c0 [0x10084f240]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyObject_MakeTpCall+0x13c [0x1007a5464]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyEval_EvalFrameDefault+0x235c [0x1008f7f1c]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyEval_Vector+0x2cc [0x1008f5918]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at method_vectorcall+0xb4 [0x1007a8f64]
Binary file "/Users/goldbaum/.pyenv/versions/3.14.0t/lib/libpython3.14t.dylib", at _PyObject_Call+0x7c [0x1007a5d40]
<truncated rest of calls>
Extension modules: numpy._core._multiarray_umath, numpy.linalg._umath_linalg, PIL._imaging, kiwisolver._cext, cython.cimports.libc.math, scipy._lib._ccallback_, scipy.linalg._fblas, scipy.linalg._flapack, _cyutility, scipy._cyutility, scipy.linalg.cython_lapack, numpy.random._common, numpy.random.bit_generator, numpy.random._bounded_integers, numpy.random._pcg64, numpy.random._mt19937, numpy.random._generator, numpy.random._philox, numpy.random._sfc64, numpy.random.mtrand, scipy.linalg._cythonized_array_utils, scipy.linalg._solve_toeplitz, scipy.linalg._decomp_lu_cython, scipy.linalg._matfuncs_schur_sqrtm, scipy.linalg._matfuncs_expm, scipy.linalg._linalg_pythran, scipy.linalg.cython_blas, scipy.linalg._decomp_update, scipy.sparse._sparsetools, _csparsetools, scipy.sparse._csparsetools, scipy.sparse.linalg._dsolve._superlu, scipy.sparse.linalg._eigen.arpack._arpack, scipy.sparse.linalg._propack._spropack, scipy.sparse.linalg._propack._dpropack, scipy.sparse.linalg._propack._cpropack, scipy.sparse.linalg._propack._zpropack, scipy.optimize._group_columns, scipy._lib.messagestream, scipy.optimize._trlib._trlib, scipy.optimize._lbfgsb, _moduleTNC, scipy.optimize._moduleTNC, scipy.optimize._slsqplib, scipy.optimize._minpack, scipy.optimize._lsq.givens_elimination, scipy.optimize._zeros, scipy._lib._uarray._uarray, scipy.special._ufuncs_cxx, scipy.special._ellip_harm_2, scipy.special._special_ufuncs, scipy.special._gufuncs, scipy.special._ufuncs, scipy.special._specfun, scipy.special._comb, scipy.linalg._decomp_interpolative, scipy.optimize._bglu_dense, scipy.optimize._lsap, scipy.spatial._ckdtree, scipy.spatial._qhull, scipy.spatial._voronoi, scipy.spatial._hausdorff, scipy.spatial._distance_wrap, scipy.spatial.transform._rotation, scipy.spatial.transform._rigid_transform, scipy.optimize._direct, matplotlib.backends._macosx (total: 67)
Code for reproduction
from concurrent.futures import ThreadPoolExecutor
import threading
from matplotlib import pyplot as plt
def run_threaded(
func,
num_threads=8,
):
"""Runs a function many times in parallel"""
with ThreadPoolExecutor(max_workers=num_threads) as tpe:
barrier = threading.Barrier(num_threads)
all_args = [(func, barrier) for i in range(num_threads)]
try:
futures = []
for arg in all_args:
futures.append(tpe.submit(*arg))
finally:
if len(futures) < num_threads:
barrier.abort()
for f in futures:
f.result()
def closure(b):
b.wait()
plt.gca()
run_threaded(closure)Actual outcome
uncaught C++ exception:
○ python test.py
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'NSWindow should only be instantiated on the main thread!'
*** First throw call stack:
(
0 CoreFoundation 0x000000019c64fae0 __exceptionPreprocess + 176
1 libobjc.A.dylib 0x000000019c112b90 objc_exception_throw + 88
2 CoreFoundation 0x000000019c674154 _CFBundleGetValueForInfoKey + 0
3 AppKit 0x00000001a05131c8 -[NSWindow _initContent:styleMask:backing:defer:contentView:] + 260
4 AppKit 0x00000001a05130b8 -[NSWindow initWithContentRect:styleMask:backing:defer:] + 48
5 _macosx.cpython-312-darwin.so 0x0000000105c67960 -[Window initWithContentRect:styleMask:backing:defer:withManager:] + 52
6 _macosx.cpython-312-darwin.so 0x0000000105c6a540 FigureManager_init + 220
7 libpython3.12.dylib 0x0000000104a80e54 wrap_init + 20
8 libpython3.12.dylib 0x0000000104a1b47c wrapperdescr_call + 380
9 libpython3.12.dylib 0x0000000104a0f8b4 _PyObject_MakeTpCall + 308
10 libpython3.12.dylib 0x0000000104b163b8 _PyEval_EvalFrameDefault + 17752
11 libpython3.12.dylib 0x0000000104a0f6ec _PyObject_FastCallDictTstate + 272
12 libpython3.12.dylib 0x0000000104a10730 _PyObject_Call_Prepend + 152
13 libpython3.12.dylib 0x0000000104a80d38 slot_tp_init + 208
14 libpython3.12.dylib 0x0000000104a790d4 type_call + 432
15 libpython3.12.dylib 0x0000000104a0f8b4 _PyObject_MakeTpCall + 308
16 libpython3.12.dylib 0x0000000104b163b8 _PyEval_EvalFrameDefault + 17752
17 libpython3.12.dylib 0x0000000104a12794 method_vectorcall + 180
18 libpython3.12.dylib 0x0000000104a0fe90 _PyVectorcall_Call + 116
19 libpython3.12.dylib 0x0000000104b16e28 _PyEval_EvalFrameDefault + 20424
20 libpython3.12.dylib 0x0000000104a1281c method_vectorcall + 316
21 libpython3.12.dylib 0x0000000104be3b1c thread_run + 92
22 libpython3.12.dylib 0x0000000104b824e4 pythread_wrapper + 28
23 libsystem_pthread.dylib 0x000000019c4f3c0c _pthread_start + 136
24 libsystem_pthread.dylib 0x000000019c4eeb80 thread_start + 8
)
libc++abi: terminating due to uncaught exception of type NSException
[1] 2332 abort python test.py
Note that this is with python 3.12 but I can reproduce this with 3.14 and 3.14t as well. Just seems to need a Mac.
Expected outcome
No crash.
Additional information
I'm guessing the MacOS backend needs some sort of locking to prevent threads from corrupting each other's state like this.
Operating system
MacOS
Matplotlib Version
3.10.7
Matplotlib Backend
macosx
Python version
Python 3.12.10 (main, Apr 28 2025, 11:48:32) [Clang 17.0.0 (clang-1700.0.13.3)]
Jupyter version
N/A
Installation
pip