[Expat-discuss] XMLParserBuffer returns no element found!!!

[Shishir.Rawat at rds.co.nz]

Hello all,

I am using DOMC 0.8.0 along with Expat 2.0.0 and crosscompiling it for ARM 
using arm-linux-g++ 3.3.2.
I am observing some problem with DOM_DocumentLS_load() API which in turn 
calls XMLParserBuffer() of Expat.
The API is returning me error code as no element found - line 1. Which i 
presume an error code of Expat rather then DOMC.
All of this happens as soon as i fork my parent process and try to call 
this API from child process. 
When i am not forking the process i get results as expected.
so when i say "make debug" it compiles without the source within #ifndef 
CONSOLE_ONLY in turn the forking stuff in main function.
This works fine and returns me appropriate results.
But when i say "make" it compiles with all the forking stuff as mentioned 
in main function.
The API returns with error "no element found: line 1".
even if i call the function function() before forking is done it returns 
me correct results.

Can anyone help me with this problem and let me know where exactly i m 
goin wrong?

The source code/makefile and xml files are as follows:

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <syslog.h>
#include <string.h>
#include <locale.h>
#include <domc.h>
#define HAVE_VARMACRO 1
#include <mba/msgno.h>

bool gRunningFlag = true ;
bool gErrorFlag = false ;
int function(void);

void signal_handler(int sig) /* signal handler function */
{
   switch(sig){
      case SIGHUP:
         /* rehash the server */
         syslog(LOG_USER | LOG_DEBUG, "Caught SIGHUP, reloading 
configuration?") ;
         break; 
      case SIGTERM:
         /* finalize the server */
         syslog(LOG_USER | LOG_DEBUG, "Caught SIGTERM, shutting down") ;
         gErrorFlag = true ;
         //exit(0) ;
         break;
      case SIGINT:
         syslog(LOG_USER | LOG_DEBUG, "Caught SIGINT, shutting down") ;
         gErrorFlag = true ;
         break ;
   } 
}

int main(int argc, char *argv[])
{
            function();

#ifndef CONSOLE_ONLY
   /* Our process ID and Session ID */
   pid_t pid, sid;
 
   /* Fork off the parent process */
   pid = fork();
   if (pid < 0) {
      exit(EXIT_FAILURE);
   }
   /* If we got a good PID, then
    * we can exit the parent process. */
   if (pid > 0) {
      exit(EXIT_SUCCESS);
   }
 
   /* Change the file mode mask */
   umask(0);
 
   /* Open any logs here */ 

   /* Create a new SID for the child process */
   sid = setsid();
   if (sid < 0) {
      /* Log the failure */
      exit(EXIT_FAILURE);
   }
 
   /* Change the current working directory */
   if ((chdir("/")) < 0) {
      /* Log the failure */
      exit(EXIT_FAILURE);
   }
 
   /* Close out the standard file descriptors */
   close(STDIN_FILENO);
   close(STDOUT_FILENO);
   close(STDERR_FILENO);
#endif

   /* install signal handlers, so we can be a well-behaved unix daemon */
   signal(SIGHUP, signal_handler);    /* hangup signal */
   signal(SIGTERM, signal_handler);   /* software termination signal from 
kill */
   signal(SIGINT, signal_handler) ;  /* Control-c or Control-Break from 
keyboard */

   while (!gErrorFlag)
   {
            function();
         /* The Big Loop */
         while (!gErrorFlag)
         {
 
            usleep(1000); /* wait 1 millisecond */
         }

      sleep(5) ;
   }
   exit(EXIT_SUCCESS);
}


int
function(void)
{
   DOM_Document *doc;
   DOM_Element *root;
   DOM_Node *node;


   if (!setlocale(LC_CTYPE, "")) {
      syslog(LOG_USER | LOG_DEBUG,  "Can't set the specified locale! "
             "Check LANG, LC_CTYPE, LC_ALL.\n");
      return 0;
   }

   doc = DOM_Implementation_createDocument(NULL, NULL, NULL);
   if (DOM_DocumentLS_load(doc, "xmlfile.xml") == -1) {
        MMSG("test xmlfile.xml load failed DOM_Exception");
      syslog(LOG_USER | LOG_DEBUG, "Error trying to load XML file \n");
      return 0;
   }

   root = doc->u.Document.documentElement;
   for (node = root->firstChild;
        node && node->nodeType != DOM_ELEMENT_NODE;
        node = node->nextSibling) {
      ;
   }
   if (node == NULL) {
      syslog(LOG_USER | LOG_DEBUG, "The document has no element 
children\n");
      return 0;
   }

   DOM_NodeList * entry = 
DOM_Document_getElementsByTagName(doc,"builddate");
   for (int i = 0 ; i < entry->length ; i++){
      DOM_Node * node = DOM_NodeList_item(entry,i);
      syslog(LOG_USER | LOG_DEBUG, "Data tag : %s :: %s", node->nodeName, 
node->firstChild->nodeValue);
   }
   DOM_Document_destroyNodeList(doc, entry, 0);

   DOM_Document_destroyNode(doc, doc);

   return 1;
}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The makefile contains

PREFIX      = /home/shishir/arm
INCLUDE = $(PREFIX)/include
LIB = $(PREFIX)/lib
CXX         = arm-linux-g++
CXX_LIBS     = -L/usr/local/arm/3.3.2/lib -L$(LIB) -pthread -ldl -lm 
-ldomc -lmba -lexpat 
CXXFLAGS    = -Wall -I$(INCLUDE)
SOURCES     =   testdomc.cpp 
OBJECTS=$(SOURCES:.cpp=.o)
EXECUTABLE=test

.SUFFIXES:      .o .cpp

.cpp.o :
        $(CXX) -c $(CXXFLAGS) $(DEBUGFLAG) -o $@ $<

all:    $(EXECUTABLE)

debug: DEBUGFLAG = -DCONSOLE_ONLY
debug:  clean all

$(EXECUTABLE):$(OBJECTS)
        $(CXX) -o $(EXECUTABLE) $(OBJECTS) $(CXX_LIBS) 
        arm-linux-strip $(EXECUTABLE)

clean:
        rm -f $(OBJECTS)
        rm -f $(EXECUTABLE)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
xmlfile.xml contains

<config>
        <builddate>2006-11-23</builddate>
</config>

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++