XML::LibXML-1.56 (was Re: XML::LibXML-1.53)

Hi,

sill me!!!

<duh>I got the subject of this thread wrong....</duh>

What I'm are debugging here is XML::LibXML-1.56 + XML::LibXSLT-1.53
(XML::LibXML-1.53 is probably fine I dunno ...)

Regards,
~/joachim

On Wednesday 10 December 2003 12:24, Joachim Bauernberger wrote:
> Hi,
>
> i just had some spare time and was able to confine the problem further to
> the PmmREFCNT_dec() function in perl-libxml-mm.c of XML-LibXML-1.56:
>
> I have added some debug printf statements to demonstrate where it crashes
>
> /* decrements the proxy counter. if the counter becomes zero or less,
>    this method will free the proxy node. If the node is part of a
>    subtree, PmmREFCNT_def will fix the reference counts and delete
>    the subtree if it is not required any more.
>  */
> int
> PmmREFCNT_dec( ProxyNodePtr node )
> {
>     xmlNodePtr libnode = NULL;
>     ProxyNodePtr owner = NULL;
>     int retval = 0;
>
>     if ( node != NULL && node) {
>         printf("## Before PmmREFCNT(node)\n");
>         retval = PmmREFCNT(node)--;
>         printf("## node->count=%d\n",node->count);
>         printf("## PmmREFCNT(node)=%d\n",PmmREFCNT(node));
>         printf("## retval=%d\n",retval);
>         if ( PmmREFCNT(node) <= 0 ) {
>             xs_warn( "NODE DELETATION\n" );
>             libnode = PmmNODE( node );
>             if ( libnode != NULL ) {
>                 if ( libnode->_private != node ) {
>                     xs_warn( "lost node\n" );
>                     libnode = NULL;
>                 }
>                 else {
>                     libnode->_private = NULL;
>                 }
>             }
>
>             PmmNODE( node ) = NULL;
>             if ( PmmOWNER(node) && PmmOWNERPO(node) ) {
>                 xs_warn( "DOC NODE!\n" );
>                 owner = PmmOWNERPO(node);
>                 PmmOWNER( node ) = NULL;
>                 if( libnode != NULL && libnode->parent == NULL ) {
>                     /* this is required if the node does not directly
>                      * belong to the document tree
>                      */
>                     xs_warn( "REAL DELETE" );
>                     PmmFreeNode( libnode );
>                 }
>                 xs_warn( "decrease owner" );
>
>               /*
>
> At this point owner is a dangling pointer which will crash when
> dereferencing it in the next call to PmmREFCNT_dec( ) -> remember this func
> is recursive ...
>               */
>
>                 printf("## Before 1 PmmREFCNT_dec(owner)\n");
>                 PmmREFCNT_dec( owner );
>
>               /* we won't get here */
>                 printf("## After 1 PmmREFCNT_dec()\n");
>             }
>             else if ( libnode != NULL ) {
>                 xs_warn( "STANDALONE REAL DELETE" );
>                 PmmFreeNode( libnode );
>             }
>             Safefree( node );
>             /* free( node ); */
>         }
>     }
>     else {
>         xs_warn("lost node" );
>     }
>     printf ("Returning retval=%d\n",retval);
>     return retval;
> }
>
>
> ~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~~~~~~~~~~~~~~~
>
> Having a quick look at the state of "owner" shows that it is probably not
> fit for being passwd around:
>
> (gdb) p *node->owner
> $10 = {_private = 0x30312f74, type = 1668183398, name = 0x6e6f6974 <Address
> 0x6e6f6974 out of bounds>, children = 0x742e73, last = 0x4015a6e8, parent =
> 0x41, next = 0x0,
>   prev = 0x0, doc = 0x0, ns = 0x0, content = 0x0, properties = 0x0, nsDef =
> 0x82eb5e8}
>
> But where does owner get srewed up in the first place? I doubt that it's
> anywhere in perl-libxml-mm.c !!
>
> I will try to look deeper into this when I have more time at hand, -> also
> I am not familiar with the code so the person who wrote this might be able
> to spot the problem faster than me ...
>
> Note that you have to add the -g switch to CFLAGS in the XML-LibXML
> Makefile to get any meaningful debugging with gdb.
>
> Cheers,
> ~/joachim
>
> On Tuesday 09 December 2003 08:55, Joachim Bauernberger wrote:
> > Hi Grant,
> >
> > On Monday 08 December 2003 18:49, Grant McLean wrote:
> > <snip/>
> >
> > > > [t][jmbdev]# perl ./10functions.t
> > > > 1..14
> > > > ok 1
> > > > ok 2
> > > > ok 3
> > > > ok 4
> > > > ok 5
> > > > ok 6
> > > > Segmentation fault
> > >
> > > One obvious difference between running 'make test' and running the test
> > > directly is that make test uses the recently built version of LibXML
> > > sitting in the blib directory whereas your simple perl command to run
> > > the test script uses the version of LibXML installed on your system.
> >
> > That version of LibXML was already installed from before, so it should
> > not make a difference (I also double checked by using the -Include
> > switches as you did below but it's all the same...)
> >
> > cheers,
> > ~/joachim
> >
> > > You could try editing the command line generated by 'make test':
> > >
> > > PERL_DL_NONLAZY=1 /usr/bin/perl -Iblib/arch -Iblib/lib \
> > > -I/usr/lib/perl/5.6.1  -I/usr/share/perl/5.6.1 t/10functions.t
> > >
> > > or you could use the 'prove' script that comes with recent versions of
> > > Test::Harness to achieve a similar thing.
> > >
> > > Of course if you've already run 'make install' then the files from blib
> > > should have been copied to /usr/local/lib already.
> > >
> > > Cheers
> > > Grant

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Web: http://www.bauernberger.org/

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