[xml] Re: Problem with XML::LibXSLT Extension function returning nodelist.

[Mike Trotman <mike trotman datalucid com>]

Thanks Tod - that sounds like it should work.

The error messges made me think that maybe the node was getting garbage 
collected twice,
but if returning a single node works then it must be something else.

Mike

Tod Harter wrote:

> I just dealt with a fairly similar problem on Linux. The only minor 
> difference being instead of throwing an error LibXSLT just sat and ate 
> 100% CPU forever on return from the callback.
>
> I discovered a few things...
>
> 1. It makes no difference what the ownership of the elements is, they 
> can just as well be unowned element nodes etc.
> 2. Your nodelist returned from the callback MUST have exactly ONE 
> node! I only tried returning element nodes, but in my case as long as 
> I returned just one node things worked fine. That returned node can 
> itself have whatever children you want.
>
> Once you get back to XSLT things should work Fine, ie something like 
> <xsl:copy-of select='myextprefix:myfunc()'/> should result in 
> inserting the one returned node and all its children.
>
> There could be various possible reasons for these problems, maybe just 
> slightly broken bindings to perl (which it seems is a fairly common 
> issue with XML::LibXSLT...) or a namespace issue, or something to do 
> with ownership of the nodes (although playing with that never did seem 
> to help in my case).
>
> Code like
>
>        my $df = XML::LibXML::NodeList->new();
>        my $e = XML::LibXML::Element->new('key');
>        $e->setAttribute('name','foobar');
>        $e->appendText('some text');
>        $df->push($e);
>        my $f = XML::LibXML::Element->new('key2');
>        $f->setAttribute('name2','foobar2');
>        $f->appendText('some text2');
>        $e->appendChild($f);
>
> use Data::Dumper;
> print "df is : ".Dumper($df)."\n";
>        return $df;
>
> definitely works for me on Linux though at this point...
>
> Mike Trotman wrote:
>
> > Hi.
> >
> > I'm not sure if this is a Perl or libxml question.
> >
> > I have an XSLT stylesheet which process multiple XML files.
> > I have added extension functions to lookup information (based on 
> > attributes in the XML) from a different, constant XML file
> > and return a nodelist of additional information which is used in a 
> > for-each loop in the XSLT.
> >
> > This all works fine in Windows XP.
> >
> > But under Linux - using variuous versions of libxml/libxslt - I get a 
> > segmentation or memory fault error:
> > E.g.
> > Recoding from TM_OUT to CM_OUT
> > .*** glibc detected *** double free or corruption (fasttop): 
> > 0x08c787e8 ***
> > Aborted
> >
> > If I set the extension functions to return an empty NodeList then I 
> > get no errors
> > (but obviously not the output I want!).
> >
> > I have also tried creating a new XML::LibXML::NodeList,
> > cloning each node found from the constant XML file,
> > setting the owner document to the current XML data
> > and pushing these nodes onto the new nodelist.
> > E.G.
> > # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> > my $dumndlist=XML::LibXML::NodeList->new();
> > # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> > my $fn_drgcombo= sub    {
> > my $tandem_UID=shift || '""';
> > my $root=shift;
> >
> > ###return $dumndlist;
> >
> > my $od=$root->get_node(0)->ownerDocument();
> > my $newl=XML::LibXML::NodeList->new();
> > my $nl=$drgcombo->findnodes('/DRGCOMBOLIST/item[ UID='.$tandem_UID.']');
> > for my $n ($nl->get_nodelist() )        {
> >        my $nn=$n->cloneNode(1);
> >        $nn->setOwnerDocument($od);
> >        $newl->push($nn);
> >        }
> >
> > return $newl;
> > };
> > # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> >
> > but I still get the memory error.
> >
> > Any idea how to return a nodelist from an extension function in 
> > XML::LibXSLT
> > (or is this a bug)?
> >
> >
> > Thanks
> >
> > Mike Trotman
> >
> >
> >
> >
> >
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