Re[2]: [libxml++] external entities substitution - libxml++ crashes

["Igor L. Smolovski" <ismolovski stbpwr com>]

Hello Christophe,

Monday, October 18, 2004, 5:29:04 PM, you wrote:

CdV> Could you post the smallest program possible that reproduce the problem
CdV> (possibly the one mentionned above) ? This would save much time for
CdV> understanding what's going wrong.

Here's the libxml2 test program that WORKS:

===test1.cpp============= BEGIN ========================================================
#include <libxml/parser.h>
#include <libxml/tree.h>
#include <string>
#include <iostream>

using namespace std;
void parse_file_test(const std::string& filename);

void parse_file_test(const std::string& filename)
{
  xmlParserCtxtPtr ctxt;
  xmlDocPtr doc;

  ctxt = xmlNewParserCtxt();
  if (ctxt == NULL) 
  {
      std::cerr << "Failed to allocate parser context" << std::endl;
      return;
  }
  
  doc = xmlCtxtReadFile(ctxt, filename.c_str(), NULL, XML_PARSE_DTDVALID | XML_PARSE_NOENT );

  if (doc == NULL) 
  {
    std::cerr << "Failed to parse " << filename << std::endl;
  } 
  else 
  {
    if (ctxt->valid == 0)
    {
      std::cerr << "Failed to validate " << filename << std::endl;
    }
    else
    {
      FILE* f = NULL;
      f = fopen("res.xml", "w");

      if (f)
      {
        xmlDocDump(f, doc);
        fclose(f);
      }
    }

    xmlFreeDoc(doc);
  }

  xmlFreeParserCtxt(ctxt);
}

int main(int _argc, char** _argv)
{
  if (_argc < 2)
  {
    cerr << "File name missing" << endl;
    return 1;
  }

  string filename(_argv[1]);

  parse_file_test(filename);
  return 0;
}

===test1.cpp============= END ========================================================

I then take the function parse_file_test() and copy-paste it to parsers/domparser.cc
and declare it in parsers/domparser.h outside the xmlpp namespace like
this:

...
#include <libxml++/api_export.h>

extern void parse_file_test(const std::string& filename);

namespace xmlpp {
...


And here's the test program I use to test parse_file_test() in libxml++:

===test2.cpp============= BEGIN ========================================================
#include <libxml++/libxml++.h>
#include <iostream>

int main(int argc, char* argv[])
{
  std::string filepath;
  if(argc > 1 )
    filepath = argv[1]; //Allow the user to specify a different XML file to parse.
  else
    filepath = "example.xml";
  
  try
  {
    parse_file_test(filepath);
  }
  catch(const std::exception& ex)
  {
    std::cout << "Exception caught: " << ex.what() << std::endl;
  }

  return 0;
}
===test2.cpp============= END ========================================================

And here's the XML files I use as input:

=====example.xml==============BEGIN=========================================
<?xml version="1.0"?>
<!DOCTYPE example PUBLIC "" "example.dtd" [
<!ENTITY wwwmurrayc SYSTEM "entity.xml">
<!ENTITY wwwlibxmlplusplus "http://libxmlplusplus.sourceforge.net";>
]>

<example>
  <examplechild id="1">
    <child_of_child>
     &wwwmurrayc;
    </child_of_child>
  </examplechild>
</example>
======example.xml=============END===========================================

======entity.xml============BEGIN===========================================
Hello!
======entity.xml============END=============================================


test1.cpp runs just fine - it produces an xml file res.xml as follows:

<?xml version="1.0"?>
<!DOCTYPE example PUBLIC "" "example.dtd" [
<!ENTITY wwwmurrayc SYSTEM "entity.xml">
<!ENTITY wwwlibxmlplusplus "http://libxmlplusplus.sourceforge.net";>
]>
<example>
  <examplechild id="1">
    <child_of_child>
     Hello!
    </child_of_child>
  </examplechild>
</example>

Alas, test2.cpp crashes. When I remove xmlFreeDoc(doc) from parse_file_test()
in libxml++, it also works just fine. Otherwise it crashes:

(gdb) bt
#0  0x00000011 in ?? ()
#1  0x0806d184 in xmlFreeNodeList (cur=0x812b070) at tree.c:3282
#2  0x0806d057 in xmlFreeNodeList (cur=0x812a4a8) at tree.c:3286
#3  0x0806d057 in xmlFreeNodeList (cur=0x8129f38) at tree.c:3286
#4  0x0806b05d in xmlFreeDoc (cur=0x8117348) at tree.c:1126
#5  0x0804c9ae in parse_file_test(std::string const&) (filename= 0xbffff7b0) at domparser.cc:277
#6  0x0804b52f in main ()
#7  0x420158d4 in __libc_start_main () from /lib/i686/libc.so.6

N.B. domparser.cc:277 - this is where xmlFreeDoc(doc) of parse_file_test() is in my case.


So what's happening? Am I doing something wrong?

-- 
Best regards,
 Igor                            mailto:ismolovski stbpwr com