Hi guys,
during the last few weeks I have been struggling quite much
in order to make PySide run with Python 3.8 at all.
The expected problems were refcounting leaks due to changed
handling of heaptypes. But in fact, the runtime behavior was
much worse, because I always got negative refcounts!
After exhaustive searching through the different 3.8 commits, I could
isolate the three problems with logarithmic search.
The hard problem was this:
Whenever PySide creates a new type, it crashes in PyType_Ready.
The reason is the existence of the Py_TPFLAGS_METHOD_DESCRIPTOR
flag.
During the PyType_Ready call, the function mro() is called.
This mro() call results in a negative refcount, because something
behaves differently since this flag is set by default in mro().
When I patched this flag away during the type_new call, everything
worked ok. I don't understand why this problem affects PySide
at all. Here is the code that would normally be only the newType line:
// PYSIDE-939: This is a temporary patch that circumvents the problem
// with Py_TPFLAGS_METHOD_DESCRIPTOR until this is finally solved.
PyObject *ob_PyType_Type = reinterpret_cast<PyObject *>(&PyType_Type);
PyObject *mro = PyObject_GetAttr(ob_PyType_Type,
Shiboken::PyName::mro());
auto hold = Py_TYPE(mro)->tp_flags;
Py_TYPE(mro)->tp_flags &= ~Py_TPFLAGS_METHOD_DESCRIPTOR;
auto *newType = reinterpret_cast<SbkObjectType *>(type_new(metatype,
args, kwds));
Py_TYPE(mro)->tp_flags = hold;
I would really like to understand the reason for this unexpected effect.
Does this ring a bell? I have no clue what is wrong with PySide, if it
is wrong at all.
Thanks -- Chris
--
Christian Tismer :^) tis...@stackless.com
Software Consulting : http://www.stackless.com/
Karl-Liebknecht-Str. 121 : https://github.com/PySide
14482 Potsdam : GPG key -> 0xFB7BEE0E
phone +49 173 24 18 776 fax +49 (30) 700143-0023
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