SIGSEGV running stubtest against PyQt5-stubs with 0.940+

[altendky]

Bug Report

When running stubtest for PyQt5-stubs we get a SIGSEGV. Bisecting PyPI published versions I see two boundaries. As of 0.940 the SIGSEGV began. As of 0.960 we started getting a few regular hint error messages prior to the SIGSEGV.

To Reproduce

I delete the venv first locally but hesitate to put recursive forced deletes where they could cause others damage.

python3.10 -m venv venv; venv/bin/pip install --upgrade pip; venv/bin/pip install . git+https://github.com/python/mypy@a9c62c5f82f34a923b8117a5394983aefce37b63 PyQt5==5.15.6 PyQt3D==5.15.5 PyQtChart==5.15.5 PyQtDataVisualization==5.15.5 PyQtNetworkAuth==5.15.5 PyQtPurchasing==5.15.5 PyQtWebEngine==5.15.5; venv/bin/stubtest --allowlist stubtest.allowlist --allowlist stubtest.allowlist.to_review --allowlist stubtest.allowlist.linux PyQt5

Expected Behavior

I expect stubtest to run without a SIGSEGV nor any other crash.

Actual Behavior

As mentioned above there are a few regular hint error messages starting with 0.960 but there's still a SIGSEGV.

error: PyQt5.Qt3DAnimation.PYQT_OPENGL_ARRAY is not present at runtime
Stub: at line 38 in file /home/altendky/repos/PyQt5-stubs/venv/lib/python3.10/site-packages/PyQt5-stubs/Qt3DAnimation.pyi
Type alias for Union[typing.Sequence[builtins.int], typing.Sequence[builtins.float], Union[builtins.bytes, builtins.bytearray, builtins.memoryview, PyQt5.sip.array[Any], PyQt5.sip.voidptr], None]
Runtime:
MISSING

error: PyQt5.Qt3DAnimation.PYQT_OPENGL_BOUND_ARRAY is not present at runtime
Stub: at line 40 in file /home/altendky/repos/PyQt5-stubs/venv/lib/python3.10/site-packages/PyQt5-stubs/Qt3DAnimation.pyi
Type alias for Union[typing.Sequence[builtins.int], typing.Sequence[builtins.float], Union[builtins.bytes, builtins.bytearray, builtins.memoryview, PyQt5.sip.array[Any], PyQt5.sip.voidptr], builtins.int, None]
Runtime:
MISSING

error: PyQt5.Qt3DAnimation.PYQT_SLOT is not present at runtime
Stub: at line 35 in file /home/altendky/repos/PyQt5-stubs/venv/lib/python3.10/site-packages/PyQt5-stubs/Qt3DAnimation.pyi
Type alias for Union[def (*Any, **Any), PyQt5.QtCore.pyqtBoundSignal]
Runtime:
MISSING

error: PyQt5.Qt3DAnimation.QAbstractAnimation is inconsistent, metaclass differs
Stub: at line 44 in file /home/altendky/repos/PyQt5-stubs/venv/lib/python3.10/site-packages/PyQt5-stubs/Qt3DAnimation.pyi
N/A
Runtime:
<class 'sip.wrappertype'>

fish: “venv/bin/stubtest --allowlist s…” terminated by signal SIGSEGV (Address boundary error)

Your Environment

• Mypy version used: 0.960 through 0.991 and a9c62c5
• Mypy command-line flags: stubtest --allowlist stubtest.allowlist --allowlist stubtest.allowlist.to_review --allowlist stubtest.allowlist.linux PyQt5
• Mypy configuration options from mypy.ini (and other config files):
  https://github.com/python-qt-tools/PyQt5-stubs/blob/15fbb1ab6f23259fba7ceca3311e322fcf397000/setup.cfg

  [mypy]
  incremental = False
  
  strict = True
  warn_unreachable = True
  ignore_missing_imports = False
  

• Python version used:
  locally tested with Python 3.10.8 (main, Oct 15 2022, 17:48:51) [GCC 9.4.0]
  observed in CI for 3.7 through 3.10

[altendky]

Installing only PyQt5, without any of the auxiliary PyQt5 packages, results in more regular hint errors but still a SIGSEGV. Just in case that ends up being a preferable situation for debugging.

rm -rf venv; python3.10 -m venv venv; venv/bin/pip install --upgrade pip; venv/bin/pip install . mypy==0.991 PyQt5==5.15.6; venv/bin/stubtest --allowlist stubtest.allowlist --allowlist stubtest.allowlist.to_review --allowlist stubtest.allowlist.linux PyQt5

[hauntsaninja]

Weird, my usual guess for segfaults is mypyc, but it looks like there's some issue in PyQt5.

Specifically, a check was added to stubtest at some point to ensure final declarations on classes that could not be subclassed. Here's a minimal repro:

>>> import PyQt5.QtBluetooth
>>> class segfault(PyQt5.QtBluetooth.QBluetooth.AttAccessConstraint): ...
... 
Fatal Python error: Segmentation fault

Current thread 0x000000020295b600 (most recent call first):
  File "<stdin>", line 1 in <module>
zsh: segmentation fault  python3

[hauntsaninja]

Here's an ad hoc stubtest patch that skips this check, in case it's useful for you:

diff --git a/mypy/stubtest.py b/mypy/stubtest.py
index 87ccbd317..0fcfa271b 100644
--- a/mypy/stubtest.py
+++ b/mypy/stubtest.py
@@ -352,6 +352,7 @@ def verify_mypyfile(
 def _verify_final(
     stub: nodes.TypeInfo, runtime: type[Any], object_path: list[str]
 ) -> Iterator[Error]:
+    return
     try:
 
         class SubClass(runtime):  # type: ignore[misc,valid-type]

I guess I could expose more stubtest configuration, but apart from that this seems like a PyQt5 thing.

[altendky]

Thanks for diagnosing this. I have reported upstream at https://www.riverbankcomputing.com/pipermail/pyqt/2022-November/045068.html though I don't know if it will get fixed as Qt5 is old and I don't know how much maintenance Phil is still doing on the PyQt5 series vs. working mostly on PyQt6.

I do tend to like configurability but I also understand that this does not seem to have caused any other issues so...

I'll look at making ourselves a small wrapper that monkey patches the _verify_final() function to be a no-op as you suggested. Thank you.

(edit: see wrapper at https://github.com/python-qt-tools/PyQt5-stubs/blob/7f86f099b8777b261df4197bec466045086fa6c3/stubtest_wrapper.py)