[Expat-discuss] segmentation fault

[Cory 'G' Watson]

The following perl crashes my mod_perl-ed apache, but seems to point to 
a bug in libexpat.  I'm using Debian's unstable 1.95.6 package.  Not 
sure why they are behind :/

(I've also cc'ed the perl-xml list, JIC)

use XML::XPath;

my $xp = XML::XPath->new(xml => "<?xml version=\"1.0\" 
encoding=\"UTF-8\" ?><config><name>Foo</name></config>");	
my $res = $xp->getNodeText("/config/name");

That segfaults my apache every time, but works find when run on the 
command line.

This seems to be caused by libexpat, and here is the gdb backtrace:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 16384 (LWP 20556)]
0x4022e245 in memmove () from /lib/libc.so.6
(gdb) bt
#0  0x4022e245 in memmove () from /lib/libc.so.6
#1  0x080e9772 in XML_GetBuffer ()
#2  0x080e95c0 in XML_Parse ()
#3  0x4036fe9d in XS_XML__Parser__Expat_ParseString ()
    from /usr/local/lib/perl/5.8.2/auto/XML/Parser/Expat/Expat.so
<snip>

Valgrind's output:

==20558== Invalid write of size 4
==20558==    at 0x4042A245: memmove (in /lib/libc-2.3.2.so)
==20558==    by 0x80E9771: XML_GetBuffer (in 
/usr/local/apache/bin/httpd)
==20558==    by 0x80E95BF: XML_Parse (in /usr/local/apache/bin/httpd)
==20558==    by 0x423D9E9C: XS_XML__Parser__Expat_ParseString (in 
/usr/local/lib/perl/5.8.2/auto/XML/Parser/Expat/Expat.so)
==20558==  Address 0x0 is not stack'd, malloc'd or free'd
==20558==
==20558== Process terminating with default action of signal 11 
(SIGSEGV): dumping core
==20558==  Address not mapped to object at address 0x0
==20558==    at 0x4042A245: memmove (in /lib/libc-2.3.2.so)
==20558==    by 0x80E9771: XML_GetBuffer (in 
/usr/local/apache/bin/httpd)
==20558==    by 0x80E95BF: XML_Parse (in /usr/local/apache/bin/httpd)
==20558==    by 0x423D9E9C: XS_XML__Parser__Expat_ParseString (in 
/usr/local/lib/perl/5.8.2/auto/XML/Parser/Expat/Expat.so)

I saw some errors before I reduced the code that pointed to a memcpy() 
in growPool, but now I'm seeing this one.  Any ideas?  Mailman is 
acting up, so I'm not yet subscribed to libexpat-discuss yet, please cc 
me.

Cory 'G' Watson

"The universal aptitude for ineptitude makes any human accomplishment 
an incredible miracle." - Dr. John Paul Stapp