Another crash-on-exit bug fixed

[Milian Wolff]

On Thursday 07 February 2013 09:48:40 Kevin Funk wrote:
> On Thursday 07 February 2013, 09:41, Kevin Funk wrote:
> > Hey,
> > 
> > I just fixed a kdelibs bug that caused KDevelop to crash on exit in case a
> > KCompositeJob was running that had subjobs with parents.
> > 
> > Easy to reproduce:
> > * Load kdevelop,kdevplatform as project
> > * Trigger build
> > * Immediately close KDevelop
> > 
> > -> Crash in ~KCompositeJobPrivate
> > 
> > Scenario:
> > * Triggering build creates a BuilderJob instance
> > 
> >   with two MakeJobs objects as subjobs
> > 
> > * Note: MakeJobs are children of MakeBuilder
> > * Both the BuilderJob object and MakeJob A are registered in the
> > runcontroller * On exit, MakeJob A is killed by the runcontroller
> > * BuilderJob object is notified about that and removes this subjob
> > * MakeJob B is still alive
> > * Eventually the MakeBuilder plugin is unloaded,
> > 
> >   ~MakeBuilder() will delete all MakeJobs ever created.
> > 
> > * Returns to event loop, BuilderJob is auto-deleted
> > * BuilderJob thinks MakeJob B is still valid and tries to delete it
> > => Double-free, crash
> > 
> > The fix in kdelibs is simple:
> > KCompositeJob assumes it has ownership over the subjobs but it doesn't
> > reparent them in addSubjob(...) -- this is now fixed in 4.11.
> > 
> > For us, this means ~MakeBuilder() no longer deletes MakeJob objects. Fixes
> > the above scenario.
> > 
> > To fix in KDevPlatform master I'd need to patch BuilderJob::addSubjob()
> > with about 3 lines of code, if you think that's worth it, I can provide a
> > patch.
> > 
> > [1] https://bugs.kde.org/show_bug.cgi?id=230692
> 
> Note that never setting a parent on a KJob instance is a valid solution as
> well (also recommended by dfaure).
> 
> Apparently KIO is doing that as well, hence the issue in KCompositeJob was
> never discovered.

Feel free to do this in KDevelop than for those who use an older KDELibs. Just 
make sure the jobs are really deleted and don't leak ;-)

Cheers
-- 
Milian Wolff
mail at milianw.de
http://milianw.de
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