[PyQt] Bug in webengine callbacks

[Kovid Goyal]

The following test script crashes, because of the callback.
Interestingly the crash only happens when the callback is on a method
of a subclass of QObject. For instance, replace w.callback below with
print and the crash goes away.

#!/usr/bin/env python3
# vim:fileencoding=utf-8

from PyQt5.Qt import *

class W(QWebEngineView):

    def callback(self, found):
        print ('result of find', found)

app = QApplication([])
w = W()
w.setHtml('<p>a</p>')
QTimer.singleShot(10, lambda: w.findText('a', QWebEnginePage.FindFlags(0), w.callback))
w.show()
app.exec_()

The relevant bit of the backtrace:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff79bea02 in method_dealloc (im=0x7ffff6bf7f88) at Objects/classobject.c:193
193     Objects/classobject.c: No such file or directory.
(gdb) bt
#0  0x00007ffff79bea02 in method_dealloc (im=0x7ffff6bf7f88) at Objects/classobject.c:193
#1  0x00007ffff79f8c0d in tupledealloc (op=0x7fffd3eb6348) at Objects/tupleobject.c:236
#2  0x00007ffff79be69f in method_call (func=0x7fffd3fa88c8, arg=0x7fffd3eb6348, kw=0x0) at Objects/classobject.c:348
#3  0x00007ffff79a9528 in PyObject_Call (func=func at entry=0x7ffff5cfb188, arg=arg at entry=0x7fffd3eaf908, kw=<optimized out>) at Objects/abstract.c:2040
#4  0x00007ffff7a56867 in PyEval_CallObjectWithKeywords (func=0x7ffff5cfb188, arg=0x7fffd3eaf908, kw=<optimized out>) at Python/ceval.c:4114
#5  0x00007fffef9f37b4 in ?? () from /usr/lib/python3.4/site-packages/sip.so
#6  0x00007fffdb2c24a8 in ?? () from /usr/lib/python3.4/site-packages/PyQt5/QtWebEngineWidgets.so
#7  0x00007fffdb09b3c9 in ?? () from /usr/lib/libQt5WebEngineWidgets.so.5

-- 
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Dr. Kovid Goyal 
http://www.kovidgoyal.net
http://calibre-ebook.com
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