[Bug 1249571] Re: Segmentation fault on Ubuntu 13.10 when using guiqwt

[Ningfei Li]

@Scott

Thanks for your reply! 
Since python-guiqwt is almost a pure python package. I don't think a rebuilding will work. I had tried it and still got that segfault.

If you step into the code when you plot, you will find that the script stucks there at this line: 
self.emit(SIG_PLOT_LABELS_CHANGED, self) in baseplot.py (in python-guiqwt directory). "self" here is a BasePlot class inherited from QwtPlot. And QwtPlot is imported as this : from PyQt4.Qwt5 import QwtPlot. I also tried to rebuild python-qwt5-qt4. But segfault again...

The signal SIG_PLOT_LABELS_CHANGED here is import from signal.py (also
in python-guiqwt directory): SIG_PLOT_LABELS_CHANGED =
SIGNAL('plot_labels_changed(PyQt_PyObject)').

The SIGNAL here is import via this: from guidata.qt.QtCore import SIGNAL. Here the python-guidata is also a pure python package, in which there exist a script QtCore.py with the following lines that might be related:
from PyQt4.QtCore import *
from PyQt4.QtCore import pyqtSignal as Signal

So that's why I think it can be a upstream problem with pyqt4...

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https://bugs.launchpad.net/bugs/1249571

Title:
  Segmentation fault on Ubuntu 13.10 when using guiqwt

Status in “python-qt4” package in Ubuntu:
  New

Bug description:
  Ubuntu 13.10
  Package: python-qt4 (4.10.3-1ubuntu1)
  Package: python-sip (4.15.2-1ubuntu1) 

  In Python, when I tried "guiqwt.tests.run()" and ran any script with
  plot function in it, it would cause the segmentation fault. But when I
  revert python-qt4 adn python-sip to the version in Ubuntu 13.04:
  python-qt4 (4.10-0ubuntu3) ) and python-sip (4.14.5-0ubuntu1),
  everything works fine.

  I traced the bug, found that: with new version of python-qt4 and
  python-sip, the guiqwt script will stuck there in this line:
  self.emit(SIG_PLOT_LABELS_CHANGED, self).

  After googling it, I find this segfault problem also affect some other users/packages:
  https://bbs.archlinux.org/viewtopic.php?id=168667
  https://bugs.archlinux.org/task/36652

  So this seems not a bug of python-guiqwt but a build problem with the
  python-qt4 and python-sip.

  I tried to build latest snapshot version of PyQt and sip and install
  them locally. But this seg fault still exist.

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