Qt 4.5.3 QList::erase() issue?

Hi,

using Qt 4.5.3 I get reproducible crashes for QList::erase().
It seems that the method returns the same iterator object, although it
shouldn't.
Here is some test code:
http://digikam3rdparty.free.fr/misc.tarballs/temp/crashy.tar.gz

Either I'm doing something totally stupid here, or Qt is broken. If I omit the
delete statement, I get a segfault, although I shouldn't get one if ::erase()
would work just fine.

If I un-comment the delete statement, it seems to work, but only because the
object the iter is pointing to is deleted and therefore the if clause is not
reached.

Can anyone confirm this?
Even with an older Qt version?

I don't want to submit a bug to Qt if I am the only one facing this problem.

Andi
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Ok removing the delete statement doesn't work, I get an infinite loop (I guess
because iter is somewhere behind the allocated QList memory now and gets
increased forever).

Andi

On Monday 12 October 2009 18:47:14 Andi Clemens wrote:

> Hi,
>
> using Qt 4.5.3 I get reproducible crashes for QList::erase().
> It seems that the method returns the same iterator object, although it
> shouldn't.
> Here is some test code:
> http://digikam3rdparty.free.fr/misc.tarballs/temp/crashy.tar.gz
>
> Either I'm doing something totally stupid here, or Qt is broken. If I omit
>  the delete statement, I get a segfault, although I shouldn't get one if
>  ::erase() would work just fine.
>
> If I un-comment the delete statement, it seems to work, but only because
>  the object the iter is pointing to is deleted and therefore the if clause
>  is not reached.
>
> Can anyone confirm this?
> Even with an older Qt version?
>
> I don't want to submit a bug to Qt if I am the only one facing this
>  problem.
>
> Andi
> _______________________________________________
> Digikam-devel mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-devel
>

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On Monday 12 October 2009 18:51:53 Andi Clemens wrote:
> Ok removing the delete statement doesn't work, I get an infinite loop (I

I mean un-commenting....

>  guess because iter is somewhere behind the allocated QList memory now and
>  gets increased forever).
>
> Andi
>
> On Monday 12 October 2009 18:47:14 Andi Clemens wrote:
> > Hi,
> >
> > using Qt 4.5.3 I get reproducible crashes for QList::erase().
> > It seems that the method returns the same iterator object, although it
> > shouldn't.
> > Here is some test code:
> > http://digikam3rdparty.free.fr/misc.tarballs/temp/crashy.tar.gz
> >
> > Either I'm doing something totally stupid here, or Qt is broken. If I
> > omit the delete statement, I get a segfault, although I shouldn't get one
> > if
> >
> >  ::erase() would work just fine.
> >
> > If I un-comment the delete statement, it seems to work, but only because
> >  the object the iter is pointing to is deleted and therefore the if
> > clause is not reached.
> >
> > Can anyone confirm this?
> > Even with an older Qt version?
> >
> > I don't want to submit a bug to Qt if I am the only one facing this
> >  problem.
> >
> > Andi
> > _______________________________________________
> > Digikam-devel mailing list
> > [hidden email]
> > https://mail.kde.org/mailman/listinfo/digikam-devel
>
> _______________________________________________
> Digikam-devel mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-devel
>

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OK!
You'll always learn new stuff.
QList::erase() will invalidate ALL iterators, so we can not save the end
iterator, like we do in the GPSSearch widget.
This is why it crashes, when the item that is deleted was the last in the
list.

I will check this with valgrind now and make sure to fix any line in digiKam
that might use such constructs.

Andi

On Monday 12 October 2009 18:55:07 Andi Clemens wrote:

> On Monday 12 October 2009 18:51:53 Andi Clemens wrote:
> > Ok removing the delete statement doesn't work, I get an infinite loop (I
>
> I mean un-commenting....
>
> >  guess because iter is somewhere behind the allocated QList memory now
> > and gets increased forever).
> >
> > Andi
> >
> > On Monday 12 October 2009 18:47:14 Andi Clemens wrote:
> > > Hi,
> > >
> > > using Qt 4.5.3 I get reproducible crashes for QList::erase().
> > > It seems that the method returns the same iterator object, although it
> > > shouldn't.
> > > Here is some test code:
> > > http://digikam3rdparty.free.fr/misc.tarballs/temp/crashy.tar.gz
> > >
> > > Either I'm doing something totally stupid here, or Qt is broken. If I
> > > omit the delete statement, I get a segfault, although I shouldn't get
> > > one if
> > >
> > >  ::erase() would work just fine.
> > >
> > > If I un-comment the delete statement, it seems to work, but only
> > > because the object the iter is pointing to is deleted and therefore the
> > > if clause is not reached.
> > >
> > > Can anyone confirm this?
> > > Even with an older Qt version?
> > >
> > > I don't want to submit a bug to Qt if I am the only one facing this
> > >  problem.
> > >
> > > Andi
> > > _______________________________________________
> > > Digikam-devel mailing list
> > > [hidden email]
> > > https://mail.kde.org/mailman/listinfo/digikam-devel
> >
> > _______________________________________________
> > Digikam-devel mailing list
> > [hidden email]
> > https://mail.kde.org/mailman/listinfo/digikam-devel
>
> _______________________________________________
> Digikam-devel mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-devel
>

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[Gilles Caulier-4]

And in QT4 api doc, it not explained ?

If no, just report it to qt irc channel... It's enough...

Gilles

2009/10/12 Andi Clemens <[hidden email]>:

> OK!
> You'll always learn new stuff.
> QList::erase() will invalidate ALL iterators, so we can not save the end
> iterator, like we do in the GPSSearch widget.
> This is why it crashes, when the item that is deleted was the last in the
> list.
>
> I will check this with valgrind now and make sure to fix any line in digiKam
> that might use such constructs.
>
> Andi
>
> On Monday 12 October 2009 18:55:07 Andi Clemens wrote:
>> On Monday 12 October 2009 18:51:53 Andi Clemens wrote:
>> > Ok removing the delete statement doesn't work, I get an infinite loop (I
>>
>> I mean un-commenting....
>>
>> >  guess because iter is somewhere behind the allocated QList memory now
>> > and gets increased forever).
>> >
>> > Andi
>> >
>> > On Monday 12 October 2009 18:47:14 Andi Clemens wrote:
>> > > Hi,
>> > >
>> > > using Qt 4.5.3 I get reproducible crashes for QList::erase().
>> > > It seems that the method returns the same iterator object, although it
>> > > shouldn't.
>> > > Here is some test code:
>> > > http://digikam3rdparty.free.fr/misc.tarballs/temp/crashy.tar.gz
>> > >
>> > > Either I'm doing something totally stupid here, or Qt is broken. If I
>> > > omit the delete statement, I get a segfault, although I shouldn't get
>> > > one if
>> > >
>> > >  ::erase() would work just fine.
>> > >
>> > > If I un-comment the delete statement, it seems to work, but only
>> > > because the object the iter is pointing to is deleted and therefore the
>> > > if clause is not reached.
>> > >
>> > > Can anyone confirm this?
>> > > Even with an older Qt version?
>> > >
>> > > I don't want to submit a bug to Qt if I am the only one facing this
>> > >  problem.
>> > >
>> > > Andi
>> > > _______________________________________________
>> > > Digikam-devel mailing list
>> > > [hidden email]
>> > > https://mail.kde.org/mailman/listinfo/digikam-devel
>> >
>> > _______________________________________________
>> > Digikam-devel mailing list
>> > [hidden email]
>> > https://mail.kde.org/mailman/listinfo/digikam-devel
>>
>> _______________________________________________
>> Digikam-devel mailing list
>> [hidden email]
>> https://mail.kde.org/mailman/listinfo/digikam-devel
>>
> _______________________________________________
> Digikam-devel mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-devel
>

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I'm talking for about 3 days in #qt channel, just because of this issue :D
And, someone just said that this is true for constBegin() / end() as well.

So I need to fix a lot of more code...

Andi

On Monday 12 October 2009 19:26:19 Gilles Caulier wrote:

> And in QT4 api doc, it not explained ?
>
> If no, just report it to qt irc channel... It's enough...
>
> Gilles
>
> 2009/10/12 Andi Clemens <[hidden email]>:
> > OK!
> > You'll always learn new stuff.
> > QList::erase() will invalidate ALL iterators, so we can not save the end
> > iterator, like we do in the GPSSearch widget.
> > This is why it crashes, when the item that is deleted was the last in the
> > list.
> >
> > I will check this with valgrind now and make sure to fix any line in
> > digiKam that might use such constructs.
> >
> > Andi
> >
> > On Monday 12 October 2009 18:55:07 Andi Clemens wrote:
> >> On Monday 12 October 2009 18:51:53 Andi Clemens wrote:
> >> > Ok removing the delete statement doesn't work, I get an infinite loop
> >> > (I
> >>
> >> I mean un-commenting....
> >>
> >> >  guess because iter is somewhere behind the allocated QList memory now
> >> > and gets increased forever).
> >> >
> >> > Andi
> >> >
> >> > On Monday 12 October 2009 18:47:14 Andi Clemens wrote:
> >> > > Hi,
> >> > >
> >> > > using Qt 4.5.3 I get reproducible crashes for QList::erase().
> >> > > It seems that the method returns the same iterator object, although
> >> > > it shouldn't.
> >> > > Here is some test code:
> >> > > http://digikam3rdparty.free.fr/misc.tarballs/temp/crashy.tar.gz
> >> > >
> >> > > Either I'm doing something totally stupid here, or Qt is broken. If
> >> > > I omit the delete statement, I get a segfault, although I shouldn't
> >> > > get one if
> >> > >
> >> > >  ::erase() would work just fine.
> >> > >
> >> > > If I un-comment the delete statement, it seems to work, but only
> >> > > because the object the iter is pointing to is deleted and therefore
> >> > > the if clause is not reached.
> >> > >
> >> > > Can anyone confirm this?
> >> > > Even with an older Qt version?
> >> > >
> >> > > I don't want to submit a bug to Qt if I am the only one facing this
> >> > >  problem.
> >> > >
> >> > > Andi
> >> > > _______________________________________________
> >> > > Digikam-devel mailing list
> >> > > [hidden email]
> >> > > https://mail.kde.org/mailman/listinfo/digikam-devel
> >> >
> >> > _______________________________________________
> >> > Digikam-devel mailing list
> >> > [hidden email]
> >> > https://mail.kde.org/mailman/listinfo/digikam-devel
> >>
> >> _______________________________________________
> >> Digikam-devel mailing list
> >> [hidden email]
> >> https://mail.kde.org/mailman/listinfo/digikam-devel
> >
> > _______________________________________________
> > Digikam-devel mailing list
> > [hidden email]
> > https://mail.kde.org/mailman/listinfo/digikam-devel
>
> _______________________________________________
> Digikam-devel mailing list
> [hidden email]
> https://mail.kde.org/mailman/listinfo/digikam-devel
>

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