Segfault in WSortFilterProxyModel::sourceDataChanged() with empty source model
Added by Jan Lindemann almost 10 years ago
Hello all,
void WSortFilterProxyModel::sourceDataChanged() crashes on me as soon as
all rows from the source model are removed. The source model emits
dataChanged(WModelIndex(), WModelIndex()), advertising a change at the
root node. Inspection of the stack trace reveals that the segfault is
triggered by accessing item->sourceRowMap_[row]. row is zero, but still
out of bounds, since sourceRowMap_ is of zero length. As the source
model doesn't have any more rows, that does look fine to me. Once that
function is invoked, and it should be, the only way around that access
and subsequent inevitable crash is a check before:
if(topLeft.parent().isValid() && !parent.isValid())
return;
but I don't see how I could possibly make that happen. I might miss
something obvious here, but I have patched the attached
safeguard into WSourceFilterProxyModel.C, which does the trick for me
and might describe what I mean.
Could somebody please shed some light on this?
Regards
Jan
Replies (4)
RE: Segfault in WSortFilterProxyModel::sourceDataChanged() with empty source model - Added by Koen Deforche almost 10 years ago
Hey Jan,
I believe the reason is that dataChanged() should not be emitted with invalid indexes. Is it your own model that does that?
The invisible root node / sentinel root index does not have any data and thus advertising data changes does not make any sense.
If rows are being removed, then that is handled by the rowsRemoved() signal.
The fix in WSortFilterProxyModel should be to ignore this event in case topLeft or bottomRight is invalid.
Regards,
koen
RE: Segfault in WSortFilterProxyModel::sourceDataChanged() with empty source model - Added by Jan Lindemann almost 10 years ago
Hi Koen,
thanks for the answer.
I believe the reason is that dataChanged() should not be emitted with
invalid indexes. Is it your own model that does that?
indeed.
If rows are being removed, then that is handled by the rowsRemoved()
signal.
Yep, that's emitted and handled fine before.
The invisible root node / sentinel root index does not have any data
and thus advertising data changes does not make any sense.
Oh, well, in my model it has, and I begin to see that it should not.
Figure stat data on a file system's root node: In the attempt to solely
use the model API to access the file system's data, I'm doing something
along the lines of
data(index, MyStatDataRole)
That works, also for the root node. I understand that advertising
changes on that node doesn't make any difference for connected Wt views,
as they don't show it. It works fine with all views and proxies,
however, with the exception of WSortFilterProxyModel, and it is also
correctly processed by non-Wt listeners to that signal.
Is putting data into the root node considered misuse of the API?
Regards
Jan
RE: Segfault in WSortFilterProxyModel::sourceDataChanged() with empty source model - Added by Koen Deforche almost 10 years ago
Hey,
I wouldn't say it's misuse, but it was clearly "unexpected". I've pushed a fix in
I've added the following in WSortFilterProxyModel which should fix the issue.
if (!topLeft.isValid() || !bottomRight.isValid())
return;
Regards,
koen
RE: Segfault in WSortFilterProxyModel::sourceDataChanged() with empty source model - Added by Jan Lindemann almost 10 years ago
Koen Deforche wrote:
I've added the following in WSortFilterProxyModel which
should fix the issue.
Cool, thanks!
Jan