[PyQt] [PyKDE] KCrash, sometimes even glibc

[Phil Thompson]

On Monday 27 August 2007, Henrik Pauli wrote:
> Hi all,
>
> Some of you might know that I'm writing a livejournal client for KDE (and
> now Qt4 too) called ljKlient...
>
> I've been trying to find the culprit for this, but I absolutely have no
> idea. The crashes don't tell me anything useful, and I've combed through
> the source files that I find relevant to the crash (for example I know that
> it doesn't tend to crash if I don't open the friendlistwindow, but that too
> isn't 100% the case!), and I found nothing that's nasty.
>
> And the thing only, ever, crashes on exit.  Never anytime else.  There are
> cases when it only crashes with py251 but doesn't with py24.  Crazy stuff.
>
> Sometimes it's just KCrash getting triggered, sometimes (only with py25)
> even glibc panics about some double-linked list having gotten corrupted.
>
> MALLOC_CHECK_=2 does not terminate the application either.
>
> Ask me any details, I'll try to tell as much as I know :)

Crashes on exit have two causes...

- PyQt bugs related to object ownership

- C++ objects being deleted in the wrong order (because Python objects are 
being garbage collected in a fairly random order).

To debug these...

- Always use current SIP and PyQt snapshots.

- Strip your application down to the bare minimum while still demonstrating 
the problem - I would expect no more than 100 lines.

- Post the example to the list as an attachment.

Phil