PyQt class name collision

class_name_collision.py

"""
If class is named as Qt class, sometimes PyQt machinery 
leads to uncaught Python exception inside sipQWidget::qt_metacast,
which leads to failed Python assertion if Python is build in debug 
mode.

$ ./python class_name_collision.py 
python: ../Objects/abstract.c:2050: PyObject_Call: Assertion `(result != ((void *)0) && !PyErr_Occurred()) || (result == ((void *)0) && PyErr_Occurred())' failed.
Aborted (core dumped)
$ gdb --args ./python class_name_collision.py 
GNU gdb (Ubuntu 7.9-1ubuntu1) 7.9
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Reading symbols from ./python...done.
(gdb) r
Starting program: /mnt/data/bob/qt/PyQt5_5.5.1_env_dbg/bin/python class_name_collision.py
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
python: ../Objects/abstract.c:2050: PyObject_Call: Assertion `(result != ((void *)0) && !PyErr_Occurred()) || (result == ((void *)0) && PyErr_Occurred())' failed.
[New Thread 0x7fffdfa3f700 (LWP 22088)]
[New Thread 0x7fffe0483700 (LWP 22087)]
[New Thread 0x7fffea8b1700 (LWP 22086)]

Program received signal SIGABRT, Aborted.
0x00007ffff6ad5cc9 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007ffff6ad5cc9 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007ffff6ad90d8 in __GI_abort () at abort.c:89
#2  0x00007ffff6aceb86 in __assert_fail_base (fmt=0x7ffff6c1f830 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", 
    assertion=assertion@entry=0x704ca8 "(result != ((void *)0) && !PyErr_Occurred()) || (result == ((void *)0) && PyErr_Occurred())", file=file@entry=0x704332 "../Objects/abstract.c", line=line@entry=2050, 
    function=function@entry=0x704f46 <__PRETTY_FUNCTION__.11058> "PyObject_Call") at assert.c:92
#3  0x00007ffff6acec32 in __GI___assert_fail (assertion=0x704ca8 "(result != ((void *)0) && !PyErr_Occurred()) || (result == ((void *)0) && PyErr_Occurred())", file=0x704332 "../Objects/abstract.c", 
    line=2050, function=0x704f46 <__PRETTY_FUNCTION__.11058> "PyObject_Call") at assert.c:101
#4  0x00000000004679a0 in PyObject_Call (func=<built-in method __instancecheck__ of type object at remote 0x7fffed02fa00>, arg=(<sip.wrappertype at remote 0x7fffed24fb40>,), kw=0x0)
    at ../Objects/abstract.c:2049
#5  0x0000000000468bf0 in PyObject_CallFunctionObjArgs (callable=<built-in method __instancecheck__ of type object at remote 0x7fffed02fa00>) at ../Objects/abstract.c:2332
#6  0x00000000004694f2 in PyObject_IsInstance (inst=<sip.wrappertype at remote 0x7fffed24fb40>, cls=<type at remote 0x7fffed02fa00>) at ../Objects/abstract.c:2522
#7  0x00007fffecd3fb70 in qpycore_qobject_qt_metacast (pySelf=0x7fffec4af718, base=0x7ffff61c2480 <sipTypeDef_QtWidgets_QWidget>, _clname=0x7fffec7b0631 <sipStrings_QtGui+35953> "QPdfWriter", 
    sipCpp=0x7fffffff9f88) at ../qpy/QtCore/qpycore_qobject_helpers.cpp:238
#8  0x00007ffff5e34945 in sipQWidget::qt_metacast (this=0xd18020, _clname=0x7fffec7b0631 <sipStrings_QtGui+35953> "QPdfWriter") at sipQtWidgetspart0.cpp:328332
#9  0x00007fffec76ef9c in QObject::inherits (this=0xd18020, classname=0x7fffec7b0631 <sipStrings_QtGui+35953> "QPdfWriter") at /home/bob/Qt/5.5/gcc_64/include/QtCore/qobject.h:422
#10 0x00007fffec5f6d03 in sipSubClass_QGuiApplication (sipCppRet=0x7fffffffa028) at /mnt/data/bob/qt/PyQt-gpl-5.5.1/sip/QtGui/qguiapplication.sip:137
#11 0x00007fffed035a2c in ?? () from /mnt/data/bob/qt/PyQt5_5.5.1_env_dbg/lib/python3.4/site-packages/sip.so
#12 0x00007fffed0421db in ?? () from /mnt/data/bob/qt/PyQt5_5.5.1_env_dbg/lib/python3.4/site-packages/sip.so
#13 0x00007ffff5dfce6d in meth_QLayout_parentWidget (sipSelf=<QVBoxLayout at remote 0x7fffec4af7d8>, sipArgs=()) at sipQtWidgetspart0.cpp:302366
#14 0x00000000004c9c0b in PyCFunction_Call (func=<built-in method parentWidget of QVBoxLayout object at remote 0x7fffec4af7d8>, arg=(), kw=0x0) at ../Objects/methodobject.c:93
#15 0x00000000005be480 in call_function (pp_stack=0x7fffffffa5a0, oparg=0) at ../Python/ceval.c:4237
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#16 0x00000000005b689e in PyEval_EvalFrameEx (f=, throwflag=0) at ../Python/ceval.c:2838
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#17 0x00000000005bbae0 in PyEval_EvalCodeEx (_co=<code at remote 0x7ffff7e47a00>, globals=, locals=0x0, args=0x7ffff61ea150, argcount=1, kws=0x0, kwcount=0, defs=0x7ffff61e3e50, defcount=1, kwdefs=0x0, 
    closure=(<cell at remote 0x7ffff7ece598>,)) at ../Python/ceval.c:3588
#18 0x00000000006f7be5 in function_call (func=<function at remote 0x7fffec458058>, arg=(<QWindow at remote 0x7fffec4af718>,), kw=0x0) at ../Objects/funcobject.c:632
#19 0x000000000046791c in PyObject_Call (func=<function at remote 0x7fffec458058>, arg=(<QWindow at remote 0x7fffec4af718>,), kw=0x0) at ../Objects/abstract.c:2040
#20 0x00000000004877a9 in method_call (func=<function at remote 0x7fffec458058>, arg=(<QWindow at remote 0x7fffec4af718>,), kw=0x0) at ../Objects/classobject.c:347
#21 0x000000000046791c in PyObject_Call (func=<method at remote 0x7ffff7eb6bb8>, arg=(), kw=0x0) at ../Objects/abstract.c:2040
#22 0x00000000004fb6a9 in slot_tp_init (self=<QWindow at remote 0x7fffec4af718>, args=(), kwds=0x0) at ../Objects/typeobject.c:6177
#23 0x00000000004e7f95 in type_call (type=0xe673a8, args=(), kwds=0x0) at ../Objects/typeobject.c:898
#24 0x000000000046791c in PyObject_Call (func=<PyQt5.QtCore.pyqtWrapperType at remote 0xe673a8>, arg=(), kw=0x0) at ../Objects/abstract.c:2040
#25 0x00000000005bf45b in do_call (func=<PyQt5.QtCore.pyqtWrapperType at remote 0xe673a8>, pp_stack=0x7fffffffc290, na=0, nk=0) at ../Python/ceval.c:4466
#26 0x00000000005be6de in call_function (pp_stack=0x7fffffffc290, oparg=0) at ../Python/ceval.c:4264
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#27 0x00000000005b689e in PyEval_EvalFrameEx (f=, throwflag=0) at ../Python/ceval.c:2838
Python Exception <class 'RuntimeError'> Type does not have a target.: 
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#28 0x00000000005bbae0 in PyEval_EvalCodeEx (_co=<code at remote 0x7ffff61c9e80>, globals=, locals=, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0, defcount=0, kwdefs=0x0, closure=0x0)
    at ../Python/ceval.c:3588
Python Exception <class 'RuntimeError'> Type does not have a target.: 
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#29 0x00000000005a67f3 in PyEval_EvalCode (co=<code at remote 0x7ffff61c9e80>, globals=, locals=) at ../Python/ceval.c:775
Python Exception <class 'RuntimeError'> Type does not have a target.: 
Python Exception <class 'RuntimeError'> Type does not have a target.: 
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#30 0x00000000004279f8 in run_mod (mod=0xbe1a20, filename=, globals=, locals=, flags=0x7fffffffdab0, arena=0xb490b0) at ../Python/pythonrun.c:2180
Python Exception <class 'RuntimeError'> Type does not have a target.: 
Python Exception <class 'RuntimeError'> Type does not have a target.: 
#31 0x0000000000427731 in PyRun_FileExFlags (fp=0xb9c940, filename_str=0x7ffff7e3cf78 "class_name_collision.py", start=257, globals=, locals=, closeit=1, flags=0x7fffffffdab0) at ../Python/pythonrun.c:2133
#32 0x0000000000425648 in PyRun_SimpleFileExFlags (fp=0xb9c940, filename=0x7ffff7e3cf78 "class_name_collision.py", closeit=1, flags=0x7fffffffdab0) at ../Python/pythonrun.c:1606
#33 0x0000000000424445 in PyRun_AnyFileExFlags (fp=0xb9c940, filename=0x7ffff7e3cf78 "class_name_collision.py", closeit=1, flags=0x7fffffffdab0) at ../Python/pythonrun.c:1292
#34 0x000000000043f254 in run_file (fp=0xb9c940, filename=0xb0c2c0 L"class_name_collision.py", p_cf=0x7fffffffdab0) at ../Modules/main.c:319
#35 0x000000000043ffea in Py_Main (argc=2, argv=0xb0a020) at ../Modules/main.c:751
#36 0x000000000041e6df in main (argc=2, argv=0x7fffffffdd38) at ../Modules/python.c:69
(gdb) frame 7
#7  0x00007fffecd3fb70 in qpycore_qobject_qt_metacast (pySelf=0x7fffec4af718, base=0x7ffff61c2480 <sipTypeDef_QtWidgets_QWidget>, _clname=0x7fffec7b0631 <sipStrings_QtGui+35953> "QPdfWriter", 
    sipCpp=0x7fffffff9f88) at ../qpy/QtCore/qpycore_qobject_helpers.cpp:238
238             if (!PyObject_IsInstance((PyObject *)pytype, (PyObject *)&qpycore_pyqtWrapperType_Type))
(gdb) list
233
234         for (SIP_SSIZE_T i = 0; i < PyTuple_GET_SIZE(mro); ++i)
235         {
236             PyTypeObject *pytype = (PyTypeObject *)PyTuple_GET_ITEM(mro, i);
237
238             if (!PyObject_IsInstance((PyObject *)pytype, (PyObject *)&qpycore_pyqtWrapperType_Type))
239                 continue;
240
241             const sipTypeDef *td = ((sipWrapperType *)pytype)->type;
242
(gdb) 
"""

from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout


class QWindow(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setLayout(QVBoxLayout())
        self.layout().parentWidget()  # <-- uncaught exception is generated and asserted here


qapp = QApplication([])
qwin = QWindow()
qwin.show()
qapp.exec()