Re: self contains no data

Hi,

A minimal test-case would be ideal!

If I was trying to debug this I would look for a place where it reliably
seg-faults, work out which Perl objects are going out of scope, then
finding where those objects first appear.

I know the findnodes() code is quite complex, so that would seem like an
obvious place to look for problems.

Otherwise, are you removing children from within a loop over
findnodes()/childNodes() ? Does the seg fault go away if you collect up
the nodes to remove then remove them outside of your loop scope?

/Tim.

On Tue, 2012-09-11 at 11:26 -0400, Bruce Miller wrote:
> A bit of followup to the problem described below.
> 
> The data corruption seems to be occurring when
>   * some XML data is found by childNodes, or findnodes, or...
>   * that data is modified, particularly with things like removeChild
>   * the data goes out of scope.
> Presumably Perl is doing cleanup, and
> either expecting non-null data, or freeing things
> that have already been freed, or...?
> 
> I'm guessing that some operations aren't clearing
> all the fields they should during modification,
> or not correctly adjusting reference counts for garbage collection.
> 
> I can write my code to dance around a bit more
> and seemingly avoid segfaults, but that doesn't
> really fix the problem.
> 
> However, I'm not sure how to proceed to find the
> actual problem. Any hints?
> 
> Thanks;
> bruce
> 
> On 09/09/2012 10:45 PM, Bruce Miller wrote:
> > Hi gang;
> >     After a long and productive, mostly uneventful, period of XML crunching
> > -- Thanks, in part, to your code & support! ---
> > I've started to see a number of segfaults occurring
> > in connection (sometimes) with a message along the lines of
> >     XML::LibXML::Node::nodeType -- self contains no data
> >
> > This happens typically after long & complex document
> > construction & manipulation, so it's hard to pinpoint
> > what exactly happened.
> >
> > My de-segfaulting skills have gotten quite rusty, and I was never so
> > good with XS, so I can only guess how to interpret what it
> > means that INT2PTR has given null.
> >
> > I've gotten a reference to an int that is no longer
> > a valid indicator of a libxml2 Node object !?!?!
> > How would I have done that?
> >
> > I realize that I noone can debug from the information
> > I've given, and it's hard for me to send a reproducible case;
> > but can anyone suggest places to start looking?
> > Is there some sort of tree-walk or validation I can
> > do to try to determine when this invalid thing might
> > have come into existence?
> >
> > FWIW, I suspect that the problem is showing up now
> > because the evolution of my code is exercising
> > XML::LibXML differently, rather than a new bug in LibXML.
> > (also it seems to occur in versions 1.90 and 2.00, maybe earlier?)
> >
> > Thanks in advance
> > bruce
> > _______________________________________________
> > Perl-XML mailing list
> > [email protected]
> > To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
> >
> 
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