[Trilinos-Users] Problems with Teuchos::XMLObject memory management?

[Kevin Long]

Hi Jonas,

I'm curious about exactly what the problem was so we can avoid it in the 
future. Did you do something like put a stack-based object into an RCP? I.e., 

XMLObject x;
RCP<XMLObject> p(&x);

That would fail. Is that what happened? 

Thanks,

Kevin

On Monday 03 March 2008 13:39, Jonas Thies wrote:
> Hi Kevin, Ross,
>
> thanks for your replies, I guess it was my fault.
> I stored some RCP's to XMLObjects within the tree so I could add more
> kids to them, and then
> when the time comes for the whole tree to depart, there is trouble.
> I now use standard pointers instead and it works
> regards,
> Jonas
>
> Kevin Long wrote:
> > Hi Jonas,
> >
> > I'm not sure what could be causing the problem. If you still can't find
> > the problem after a clean rebuild and valgrind/purify, perhaps you could
> > send me a stripped-down example showing the problem and I could have a go
> > at debugging it. I'm the guy who originally wrote the class, and so would
> > be happy to try to fix it. It's been years since I wrote it so it's
> > hardly fresh in my mind, but I can probably figure out how it works :-).
> >
> > As Ross said, this class is used heavily without incident so I'd be
> > surprised if there's a problem; however, it may be you're using some
> > not-often-used feature in which a bug has lurked silently for years.
> >
> > Let me know how it goes, and drop a line if you need me to help with the
> > debugging.
> >
> > Kevin
> >
> > On Monday 03 March 2008 07:19, Bartlett, Roscoe A wrote:
> >> Hello Jonas,
> >>
> >> The class XMLObject is a handle class that does shallow copies of the
> >> XMLObjectImplen data by default.  That is why where is no specifically
> >> defined copy constructor or assignment operator, or destructor; the
> >> compiler-generated versions should do exactly the right thing since only
> >> a single Teuchos::RCP is being stored as private data.  When you use a
> >> shallow-copy handle class you have to be very careful about sharing
> >> issues and call deepCopy() when that is what you want.  I did not write
> >> this class and there is just one simple unit test for it (see
> >> teuchos/test/XML/cxx_main.cpp) but this class has seen very heavy use in
> >> the last few years and we have need seen issues like what you describe.
> >>
> >> Have you run valgrind or purify on your program?  The final segfault
> >> that you are seeing might be a result of other code that is corrupting
> >> the data of the XMLObject[Implem] objects.  The first that you should
> >> always do when you get a segfault is to delete all of the *.o, *.a, and
> >> *.exe files and rebuild everything from scratch.  That fixes about 50%
> >> of the segfaults that I have seen in the past.
> >>
> >> I hope some of these ideas help,
> >>
> >> Ross
> >>
> >> -----Original Message-----
> >> From: trilinos-users-bounces at software.sandia.gov
> >> [mailto:trilinos-users-bounces at software.sandia.gov] On Behalf Of Jonas
> >> Thies Sent: Monday, March 03, 2008 2:14 AM
> >> Cc: trilinos-users at software.sandia.gov
> >> Subject: [Trilinos-Users] Problems with Teuchos::XMLObject memory
> >> management?
> >>
> >> Hi all,
> >>
> >> I'm trying to put together a fairly complicated XML structure to be used
> >> as the 'light-weight' part of an Xdmf output format. All goes well until
> >> the end of the run, when the XMLObject is being deleted, whereupon I get
> >> a coredump. It seems that there is an issue with the internal
> >> std::vector destructor. When I put everything in one main program it
> >> works, I suspect it has to do with the way new XMLObjects are copied
> >> into the vector. I noticed that there is a method 'deepCopy', but no
> >> copy constructor, which might explain the behaviour (std::vector
> >> push_back calls the copy constructor). Am I doing something wrong? I'm
> >> surprised it works for the XMLParameterListWriter class. Is there an
> >> example somewhere? By the way, I'm working with Trilinos version 8.0.1
> >>
> >> thanks for your help,
> >> Jonas
> >>
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>
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-- 
Dr. Kevin Long
Department of Mathematics and Statistics
Texas Tech University
Lubbock TX 79409
kevin.long at ttu.edu