Core dump while running with free-threaded interpreters

[clin1234]

Encountered while building docs of greenlet at my fork: https://github.com/clin1234/greenlet/actions/runs/19298611298/job/55197779501

sphinx-build -b doctest -d docs/_build/doctrees2 docs docs/_build/doctest2
  shell: /usr/bin/bash -e {0}
  env:
    PYTHONHASHSEED: 1042466059
    ZOPE_INTERFACE_STRICT_IRO: 1
    PYTHONUNBUFFERED: 1
    PYTHONDONTWRITEBYTECODE: 1
    PYTHONDEVMODE: 1
    PYTHONFAULTHANDLER: 1
    PIP_UPGRADE_STRATEGY: eager
    PIP_NO_WARN_SCRIPT_LOCATION: 1
    TWINE_USERNAME: __token__
    pythonLocation: /opt/hostedtoolcache/Python/3.14.0/x64-freethreaded
    PKG_CONFIG_PATH: /opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/pkgconfig
    Python_ROOT_DIR: /opt/hostedtoolcache/Python/3.14.0/x64-freethreaded
    Python2_ROOT_DIR: /opt/hostedtoolcache/Python/3.14.0/x64-freethreaded
    Python3_ROOT_DIR: /opt/hostedtoolcache/Python/3.14.0/x64-freethreaded
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib
Running Sphinx v8.2.3
loading translations [en]... done
making output directory... done
Converting `source_suffix = '.rst'` to `source_suffix = {'.rst': 'restructuredtext'}`.
loading intersphinx inventory 'python' from https://docs.python.org/objects.inv ...
loading intersphinx inventory 'gevent' from https://www.gevent.org/objects.inv ...
intersphinx inventory has moved: https://docs.python.org/objects.inv -> https://docs.python.org/3/objects.inv
building [mo]: targets for 0 po files that are out of date
writing output... 
building [doctest]: targets for 15 source files that are out of date
updating environment: [new config] 15 added, 0 changed, 0 removed
<frozen importlib._bootstrap>:491: RuntimeWarning: The global interpreter lock (GIL) has been enabled to load module 'greenlet._greenlet', which has not declared that it can run safely without the GIL. To override this behavior and keep the GIL disabled (at your own risk), run with PYTHON_GIL=0 or -Xgil=0.
reading sources... [  7%] api
reading sources... [ 13%] c_api
reading sources... [ 20%] caveats
reading sources... [ 27%] changes
reading sources... [ 33%] contextvars
reading sources... [ 40%] creating_executing_greenlets
reading sources... [ 47%] development
reading sources... [ 53%] greenlet
reading sources... [ 60%] greenlet_gc
reading sources... [ 67%] gui_example
reading sources... [ 73%] history
reading sources... [ 80%] index
reading sources... [ 87%] python_threads
reading sources... [ 93%] switching
reading sources... [100%] tracing
CHANGES.rst:26: WARNING: Mismatch: both interpreted text role prefix and reference suffix. [docutils]
CHANGES.rst:3: WARNING: Duplicate explicit target name: "pr". [docutils]
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
copying assets... 
copying assets: done
running tests...

Document: contextvars
---------------------
1 item passed all tests:
  18 tests in default
18 tests in 1 item.
18 passed.
Test passed.

Document: creating_executing_greenlets
--------------------------------------
1 item passed all tests:
  38 tests in default
38 tests in 1 item.
38 passed.
Test passed.

Document: greenlet
------------------
1 item passed all tests:
  17 tests in default
17 tests in 1 item.
17 passed.
Test passed.

Document: greenlet_gc
---------------------
1 item passed all tests:
  30 tests in default
30 tests in 1 item.
30 passed.
Test passed.

Document: gui_example
---------------------
1 item passed all tests:
  14 tests in default
14 tests in 1 item.
14 passed.
Test passed.

Document: python_threads
------------------------
1 item passed all tests:
  16 tests in default
16 tests in 1 item.
16 passed.
Test passed.

Document: switching
-------------------
1 item passed all tests:
  16 tests in default
16 tests in 1 item.
16 passed.
Test passed.

Document: tracing
-----------------
1 item passed all tests:
   9 tests in default
9 tests in 1 item.
9 passed.
Test passed.

Doctest summary
===============
  158 tests
    0 failures in tests
    0 failures in setup code
    0 failures in cleanup code
build succeeded, 2 warnings.

Testing of doctests in the sources finished, look at the results in docs/_build/doctest2/output.txt.
Fatal Python error: Segmentation fault

Current thread 0x00007f1812a97b80 [sphinx-build] (most recent call first):
  <no Python frame>

Current thread's C stack trace (most recent call first):
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at _Py_DumpStack+0x47 [0x7f181255d9c5]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x166d80 [0x7f1812566d80]
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", at +0x45330 [0x7f1812045330]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at _Py_MergeZeroLocalRefcount+0x29 [0x7f18125e7609]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x1dc555 [0x7f18125dc555]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at PyDict_SetItem+0xd5 [0x7f18125db9e5]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x1e743d [0x7f18125e743d]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x2face3 [0x7f18126face3]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x150be2 [0x7f1812550be2]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at Py_Exit+0x3b [0x7f18126faf0b]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x2fdcbb [0x7f18126fdcbb]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x2fdade [0x7f18126fdade]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x153c55 [0x7f1812553c55]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at +0x2fd5b8 [0x7f18126fd5b8]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at Py_RunMain+0x414 [0x7f1812706e64]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/lib/libpython3.14t.so.1.0", at Py_BytesMain+0x3b [0x7f18127068fb]
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", at +0x2a1ca [0x7f181202a1ca]
  Binary file "/lib/x86_64-linux-gnu/libc.so.6", at __libc_start_main+0x8b [0x7f181202a28b]
  Binary file "/opt/hostedtoolcache/Python/3.14.0/x64-freethreaded/bin/python", at _start+0x25 [0x56498a41c095]
/home/runner/work/_temp/d0b62f78-400a-45cb-8fcd-ce92ae14cbf1.sh: line 1:  2917 Segmentation fault      (core dumped) sphinx-build -b doctest -d docs/_build/doctrees2 docs docs/_build/doctest2
Error: Process completed with exit code 139.

[AA-Turner]

This line looks suspect:

<frozen importlib._bootstrap>:491: RuntimeWarning: The global interpreter lock (GIL) has been enabled to load module 'greenlet._greenlet', which has not declared that it can run safely without the GIL. To override this behavior and keep the GIL disabled (at your own risk), run with PYTHON_GIL=0 or -Xgil=0.

Can greenlet run with the GIL disabled? Do the tests pass without segfaults? The doctest builder runs code from the given library, so I would look there first.

Sphinx runs in CI under the free-threaded build, so I'm not aware of any core issues.

A

[clin1234]

This line looks suspect:

<frozen importlib._bootstrap>:491: RuntimeWarning: The global interpreter lock (GIL) has been enabled to load module 'greenlet._greenlet', which has not declared that it can run safely without the GIL. To override this behavior and keep the GIL disabled (at your own risk), run with PYTHON_GIL=0 or -Xgil=0.

Can greenlet run with the GIL disabled? Do the tests pass without segfaults? The doctest builder runs code from the given library, so I would look there first.

Sphinx runs in CI under the free-threaded build, so I'm not aware of any core issues.

A

Odd that when running the command inside a Codespace with a free-threaded interpreter from deadsnakes, no core dump occurs.