Memory Leak related with replaceChild

Question

Here is source code of my function:

bool FieldModel::updateNode(QDomNode &node,const QString &parent){

  QDomElement rootOfTag;

  rootOfTag=fieldState.firstChild().firstChildElement(parent);

  qDebug()<<"Before"<<fieldState.toString();
  QDomNodeList sameTags=rootOfTag.elementsByTagName(node.firstChild().toElement().tagName());
  for(uint i=0;i<sameTags.length();i++){
      QDomNode nodeToReplace=sameTags.item(i);
      if(nodeToReplace.toElement().attribute("id")==node.firstChild().toElement().attribute("id")){
        nodeToReplace.parentNode().replaceChild(node,nodeToReplace);//Cause Memory Leak
        qDebug()<<"After"<<fieldState.toString();
        return true;
      }
  }

insertNode(node,parent);
return true;
}

Memory usage of this my program strictly increases, but when I removed line nodeToReplace.parentNode().replaceChild(node,nodeToReplace);, program uses stable amount of memory. I monitored fieldState(QDomDocument), and it is not growing while I'm using replaceChild (I make small changes). What can be problem?

Thanks.

Answer 1

The docs say the call returns a reference to the old, replaced node on success:

Returns a new reference to oldChild on success or a null node an failure.

I don't know QT well but I'd guess it assumes you'll clean the old node reference up?

Answer 2

Looks like a QDom bug to me (which wouldn't surprise me too much, just submitted a patch to make "<a:>foo</a:>" not crash QDom). Try with a minimal example. If that still leaks and if are on Linux or OS X, you could run it in valgrind. Both the example and valgrind output would make a good bug report.

Edit: Would be interesting if removeChild() also leaks for you