Dear mailing list,
I've come across a strange problem leading to very problematic
segmentation faults. Reading here and there I came to the conclusion
that the problem is somehow linked to some ownership issues.
And this proved quite a good idea => no more segmentation faults.
However, in the process of debugging that issue I wrote the
following piece of code, which crashes. My problem is that
I don't understand why it crashes... It'd be nice if someone
could explain in order to make sure my understanding
of the issue is right.
My best explanation is that the selection model is not
created by PySide but inside Qt. Therefore, somehow, PySide
can't get a hold of it and can't handle its destruction
properly, leaving to leaks...
I use :
- python 2.7.2
- PySide-1.0.5qt473-py2.7
- Windows XP
Thank you,
Stefan
Here comes the code (please note that I have already added it
to bug #1041 at [1]; I've also read [2] but it doesn't seem to
cover this specific issue )
import sys
from PySide.QtGui import *
from PySide.QtCore import *
class BugWindow(QMainWindow):
def __init__(self):
super(BugWindow,self).__init__()
# First (not so important) question : who has ownership
# on the table here ? Python or Qt ? Qt doc says
# that QMainWindow takes ownership of the table but since
# we're in a subclass then, who has ownership ? The
# subclass (and thus Python) or the parent class ?
self.setCentralWidget(QTableView())
# We're going to call test_bug() often and until death
# It's just one way of doing this
self.timer = QTimer(self)
self.timer.timeout.connect(self.test_bug)
# Adapt this to the performance of your system if needed
# to make sure you exit test_bug() before it is called
# again.
self.timer.start(20)
@Slot()
def test_bug(self):
# First, create a new model ----------------------------------------
# If there was a model in self.m before, it is now
# ready for garbage collection => if something
# happens now on the table that requires access
# to the model, we're in for a possible bug
# parent is None => ownership by Python (and then
# destruction when leaving this method) ?
self.m = QStandardItemModel(1,1,None)
# Set the table's model --------------------------------------------
table = self.centralWidget()
# A new selection model is associated by Qt to the model, cf Qt. doc
# Question is : what happened to the previous selection model ?
table.setModel(self.m) # model's ownership is left unchanged, cf. Qt
doc.
# Here, I expect the old model to be definitely
# lost (it is not in self.m anymore and it is
# not referenced by the table anymore). Therefore
# the model can be garbage collected by Python.
# But for some reason, adding this line makes the
# program crash after a few calls to test_bug()
table.selectionModel()
# Interestingly, the following line doesn't crash
# However, it sounds normal. By setting the parent
# to None, I guess the ownership is transferred
# from Qt (which created the selection model) to
# Python (question is : is my guess right ?)
# table.selectionModel().setParent(None)
print "go !"
app = QApplication(sys.argv)
window = BugWindow()
window.show()
app.exec_()
When the crash occurs, the output looks lilke this :
C:\PORT-STC\pl\ECLIPS~1\PL\src>python bug.py
go !
go !
go !
go !
go !
go !
Object::connect: No such signal
QItemSelectionModel::rowsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::headerDataChanged(Qt::Orientation,int,int)
Object::connect: No such signal QItemSelectionModel::layoutAboutToBeChanged()
Object::connect: No such signal
QItemSelectionModel::dataChanged(QModelIndex,QModelIndex)
Object::connect: No such signal
QItemSelectionModel::headerDataChanged(Qt::Orientation,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsInserted(QModelIndex,int,int)
Object::connect: No such signal QItemSelectionModel::modelReset()
Object::connect: No such signal QItemSelectionModel::layoutChanged()
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeInserted(QModelIndex,int,int)
Object::connect: No such signal QItemSelectionModel::layoutAboutToBeChanged()
Object::connect: No such signal QItemSelectionModel::layoutChanged()
Object::connect: No such signal
QItemSelectionModel::columnsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::headerDataChanged(Qt::Orientation,int,int)
Object::connect: No such signal QItemSelectionModel::layoutAboutToBeChanged()
Object::connect: No such signal
QItemSelectionModel::dataChanged(QModelIndex,QModelIndex)
Object::connect: No such signal
QItemSelectionModel::headerDataChanged(Qt::Orientation,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsInserted(QModelIndex,int,int)
Object::connect: No such signal QItemSelectionModel::modelReset()
Object::connect: No such signal QItemSelectionModel::layoutChanged()
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeInserted(QModelIndex,int,int)
Object::connect: No such signal QItemSelectionModel::layoutAboutToBeChanged()
Object::connect: No such signal QItemSelectionModel::layoutChanged()
Object::connect: No such signal
QItemSelectionModel::dataChanged(QModelIndex,QModelIndex)
Object::connect: No such signal
QItemSelectionModel::headerDataChanged(Qt::Orientation,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsInserted(QModelIndex,int,int)
Object::connect: No such signal QItemSelectionModel::modelReset()
Object::connect: No such signal QItemSelectionModel::layoutChanged()
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeRemoved(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::rowsAboutToBeInserted(QModelIndex,int,int)
Object::connect: No such signal
QItemSelectionModel::columnsAboutToBeInserted(QModelIndex,int,int)
Object::connect: No such signal QItemSelectionModel::layoutAboutToBeChanged()
Object::connect: No such signal QItemSelectionModel::layoutChanged()
Error calling slot "test_bug"
Traceback (most recent call last):
File "bug.py", line 71, in test_bug
table.setModel(self.m) # model's ownership is left unchanged, cf. Qt doc.
AttributeError: 'PySide.QtGui.QItemSelectionModel' object has no attribute
'rowCount'
Object::disconnect: No such signal
QItemSelectionModel::rowsInserted(QModelIndex,int,int)
[1] http://bugs.pyside.org/show_bug.cgi?id=1041
[2] https://github.com/PySide/PySide/pull/93
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