Bug 892 – Segfault when destructing QWidget and QApplication has event filter installed

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Bug 892 - Segfault when destructing QWidget and QApplication has event filter installed

Summary:

Segfault when destructing QWidget and QApplication has event filter installed

Status:	CLOSED FIXED

Product:	PySide
Classification:	Unclassified
Component:	PySide
Version:	1.0.3
Platform:	PC Linux

Importance:	P1 normal
Assigned To:	Hugo Parente Lima

URL:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2011-06-18 00:01 EEST by Catalin Drula
Modified:	2011-07-22 22:12 EEST (History)
CC List:	10 users (show)

See Also:

Attachments
Stack trace for crash on Lucid with PySide 1.0.3 (3.78 KB, text/plain) 2011-06-18 00:01 EEST, Catalin Drula	Details
Short example that reproduces segmentation fault (635 bytes, text/x-python) 2011-06-19 22:22 EEST, Catalin Drula	Details
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Description Catalin Drula 2011-06-18 00:01:59 EEST

Created attachment 350 [details]
Stack trace for crash on Lucid with PySide 1.0.3

I consistently get segmentation faults with Ubuntu 10.04.2 LTS (Lucid) and
PySide 1.0.3 when widgets/dialogs are garbage collected.

The following function:

    def close(self):       
        box = QMessageBox()
        box.setStandardButtons(QMessageBox.Save | QMessageBox.Discard |
QMessageBox.Cancel)
        box.setText("There are unsaved changes to the current session.")
        box.setInformativeText("Do you want to save your changes?")
        ret = box.exec_()

        if ret == QMessageBox.Discard:
            return "OK"

consistently produces segmentation faults when it returns as a result of the
deallocation of the QMessageBox object.

This problem never occurs with Ubuntu 10.10 (Maverick) and PySide 1.0.1. I
wasn't able yet to do a more detailed regression as I could not find the older
PySide .deb packages (1.0.2 or 1.0.1). I'll try next Maverick with 1.0.3 and
publish the results here.

Here are the final lines of the relevant stack trace (a more detailed trace is
attached):

(gdb) bt
#0  0x0203877e in QWidget::~QWidget() () from /usr/lib/libQtGui.so.4
#1  0x0174fb95 in Shiboken::callCppDestructor<QMessageBox> (cptr=0x0) at
/usr/include/shiboken/basewrapper.h:106
#2  0x00c9b465 in SbkDeallocWrapper (pyObj=<PySide.QtGui.QMessageBox at remote
0xa940d4c>) at /build/buildd/shiboken-1.0.3/libshiboken/basewrapper.cpp:188
#3  0x080a8a44 in tupledealloc (op=0xa92a8ac) at ../Objects/tupleobject.c:170
#4  0x0108c5c3 in ~AutoDecRef (this=0xabd2df0, arg__1=0xaa5ce50,
arg__2=0xbfe98fe4) at /usr/include/shiboken/autodecref.h:47

Comment 1 Catalin Drula 2011-06-19 22:22:27 EEST

Created attachment 351 [details]
Short example that reproduces segmentation fault

Comment 2 Catalin Drula 2011-06-19 22:25:17 EEST

I've added a short example that reproduces the segmentation fault. It is
related to the event filter installed on QApplication.instance().

The same example does not segfault on Maverick with Pyside 1.0.1.

An equivalent C++ example does not crash on either Lucid (Qt 4.6) or Maverick
(Qt 4.7).

Comment 3 Hugo Parente Lima 2011-06-20 20:47:22 EEST

Thanks for catching this regression for us and sorry for their existence.

Comment 4 Catalin Drula 2011-06-20 20:57:34 EEST

I've finally managed to get some more data points with Didier's help (perhaps a
more permanent system for making older builds available would be a good idea).

Seg fault: Lucid/Maverick, 1.0.3
No crash: Lucid - 1.0.2, Maverick - 1.0.1

So it seems that the problem was introduced in 1.0.3

Comment 5 Hugo Parente Lima 2011-06-23 00:10:11 EEST

Fixed in commit:

shiboken/67561024f2e0ad69e482ecf5e5e3ff4be944f169

Comment 6 Hugo Parente Lima 2011-06-27 19:53:14 EEST

*** Bug 894 has been marked as a duplicate of this bug. ***

Comment 7 renato filho 2011-07-22 22:12:48 EEST

release 1.0.5