[PyQt] Basic QML test seg faults in PyQT but not QT on Linux

[Louis Simons]

Additionally, my seg. fault seems to be tied both to PyQT (as opposed to
the C++ API) and the graphics drivers (for an NVIDIA GeForce GTS 250).  I
tried switching to Linux Mint's xserver-xorg-video-nouveau driver, and
while that didn't work and fell back to software rendering, the application
worked in both PyQT and C++.  When I switched back to the recommended
driver, nvidia-340 (340.96-0ubuntu3), the seg. fault in the PyQT version
came back.

Is there a way to figure out exactly what differs between the C++ and PyQT
versions using GDB?

Thanks,
Louis

On Sat, Sep 17, 2016 at 5:04 PM Louis Simons <lousimons at gmail.com> wrote:

> On 17 Sep 2016, at 2:39 am, Louis Simons <lousimons at gmail.com> wrote:
>> >
>> >
>> > Ok.  I'm hoping someone on Linux will chime in for confirmation.  This
>> seg. fault doesn't make sense as there's definitely people using QML in
>> PyQT in recent versions.  Is there anyway to identify the source of the
>> seg. fault?
>> >
>> > I added the backtrace to
>> http://stackoverflow.com/questions/39381009/simple-pyqt5-qml-application-causes-segmentation-fault.
>> It all seems to be a result of __strstr_sse2 receiveing a null pointer from
>> haystack_start.  While this seems like a graphics driver bug (
>> https://bugs.kde.org/show_bug.cgi?id=348812), it works in the C++
>> version, so is it possible there's a problem in a PyQT binding?
>>
>> Unlikely.
>>
>
> I agree it's unlikely, but if the exact same C++ program works without a
> seg. fault, and the PyQT version crashes, what else could it be?  The C++
> is the following:
>
>     #include <QGuiApplication>
>     #include <QQmlApplicationEngine>
>
>     int main(int argc, char *argv[]) {
>         QGuiApplication app(argc, argv);
>         QQmlApplicationEngine engine;
>         engine.load(QUrl(QStringLiteral("simple.qml")));
>         return app.exec();
>     }
>
> The Python is the following:
>
>     from sys import argv, exit
>     from PyQt5.QtGui import QGuiApplication
>     from PyQt5.QtQml import QQmlApplicationEngine
>
>     def main():
>         app = QGuiApplication(argv)
>         engine = QQmlApplicationEngine()
>         engine.load('simple.qml')
>         exit(app.exec_())
>
>     if __name__ == '__main__':
>         main()
>
> Thanks,
> Louis
>
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