[PyQt] interpreter shutdown crash (QAccessibleCache)

[Erik Hvatum]

Is there something special wrt to deallocation of the global
QAccessibleCache instance upon interpreter exit?  Perhaps related to
QObject.destroyed signal connections?

If I instantiate a particular custom PyQt5 widget as a top-level window
that, itself, has lots of child widgets, the interpreter will tend to crash
at on exit.  The only reliable method I have found for avoiding this crash
is to ensure that no outstanding references to my custom widget instance
remain and then to issue a gc.collect() call before exiting.

The PyQt5 docs suggest that I really shouldn't have to worry about on-exit
deallocation crashes so long as a module-level reference to my top-level
PyQt5 widget exist when exiting the interpreter.  However, I'm experiencing
the opposite.  Incidentally, the pySelf pointer argument to the
qpycore_qobject_metaobject call at the top of the stack trace pasted below
appears to point to junk.

Any advice or tips would be great!  Failing that, in the morning, I'm going
to try eliminating all references to the QObject.destroyed signal from my
code, since I have a feeling connections to that signal are what
~QAccessibleCache is attempting to tear down when the crash occurs.

Stack trace (it is similar on OS X with release builds of PyQt5, cpython,
Qt5):

QtCore_d.pyd!qpycore_qobject_metaobject(_sipSimpleWrapper * pySelf,
_sipTypeDef * base) Line 52    C++
QtWidgets_d.pyd!sipQTableView::metaObject() Line 557    C++
Qt5Cored.dll!QObject::~QObject() Line 1003    C++
Qt5Guid.dll!QAccessibleCache::~QAccessibleCache()    C++
Qt5Guid.dll!QAccessibleCache::`vector deleting destructor'(unsigned int)
C++
Qt5Guid.dll!``anonymous
namespace'::Q_QGS_qAccessibleCache::innerFunction'::`8'::Cleanup::~Cleanup()
Line 46    C++
Qt5Guid.dll!``anonymous
namespace'::Q_QGS_qAccessibleCache::innerFunction'::`9'::`dynamic atexit
destructor for 'cleanup''()    C++
Qt5Guid.dll!_CRT_INIT(void * hDllHandle, unsigned long dwReason, void *
lpreserved) Line 416    C
Qt5Guid.dll!__DllMainCRTStartup(void * hDllHandle, unsigned long dwReason,
void * lpreserved) Line 522    C
Qt5Guid.dll!_DllMainCRTStartup(void * hDllHandle, unsigned long dwReason,
void * lpreserved) Line 473    C
ntdll.dll!0000000077153a81()    Unknown
ntdll.dll!0000000077153890()    Unknown
msvcr120d.dll!000007fedf974eeb()    Unknown
msvcr120d.dll!000007fedf97595f()    Unknown
msvcr120d.dll!000007fedf975986()    Unknown
python_d.exe!__tmainCRTStartup() Line 662    C
python_d.exe!wmainCRTStartup() Line 466    C
kernel32.dll!0000000076f25a4d()    Unknown
ntdll.dll!000000007715b831()    Unknown

Thanks,
Erik
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