[Qt-interest] QtScript segfault on C++ signal (dis)connection/firing

[Sean M. Pappalardo]

Hello again.

Just wondering if you've been able to find anything out? This issue is
quite literally a show-stopper, considering this is a DJ app. :)

After a bunch more testing, the crashing doesn't happen if I don't
connect any of the C++ signals. I can call MidiScriptEngine::setValue()
all day from the script with no problems. It's crashing when signals are
connected and setValue() is called many times in a row, affecting
objects that emit signals. And it's worse on faster systems (more
setValue()s per second, I assume.) The signals only fire once per
latency period though. I did also find that increasing the latency alot
(400ms or more) makes it less likely to happen, depending on processor
speed.

I ran valgrind with Mixxx compiled against Qt 4.5 which seems to give
more detail in the QtScript area, incase it helps:

=20125== Process terminating with default action of signal 11 (SIGSEGV)
==20125==  Access not within mapped region at address 0x8
==20125==    at 0x530F078:
QScriptContextPrivate::execute(QScript::Code*) (qscriptcontext_p.cpp:2020)
==20125==    by 0x5320B15:
QScript::ScriptFunction::execute(QScriptContextPrivate*)
(qscriptcontext_p.cpp:313)
==20125==    by 0x5335B7A: QScriptEnginePrivate::call(QScriptValueImpl
const&, QScriptValueImpl const&, QList<QScriptValueImpl> const&, bool)
(qscriptengine_p.cpp:1252)
==20125==    by 0x5371496: QScriptValue::call(QScriptValue const&,
QList<QScriptValue> const&) (qscriptvalueimpl_p.h:719)
==20125==    by 0x80FA4C1: MidiObject::receive(MidiCategory, char, char,
char, QString) (midiobject.cpp:273)
==20125==    by 0x81BA89F: MidiObjectALSASeq::run()
(midiobjectalsaseq.cpp:286)
==20125==    by 0x502861D: QThreadPrivate::start(void*)
(qthread_unix.cpp:184)
==20125==    by 0x42CB4BF: start_thread (in
/lib/i686/cmov/libpthread-2.7.so)
==20125==    by 0x55B461D: clone (in /lib/i686/cmov/libc-2.7.so)

Thanks again for your time. Let me know your thoughts and if there's
anything else I can do to help.

Sincerely,
Sean M. Pappalardo

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