TinyXml2 XMLDocument parse after create new Element crash

Question

In TinyXmlv1 i can create a temp Xml Element then Parse document by

TiXmlDocument doc;
TiXmlElement * element = new TiXmlElement( "Hello" );
TiXmlText * text = new TiXmlText( "World" );
element->LinkEndChild( text );
doc.Parse("<TAGS></TAGS>"); // It OK

Now i want switch to TinyXmlv2 by following:

#include "tinyxml2.h"

using namespace tinyxml2;

int main(int argc, char* argv[])
{
    tinyxml2::XMLDocument doc;
    tinyxml2::XMLElement* newElm = doc.NewElement("Hello");
    newElm->SetText("World");

    doc.Parse("<TAGS></TAGS>"); // This will crash

    return 0;
}

I cant understand why it crash.

Answer 1

It's not a "crash" but an assert from tinyxml2 because you are "throwing away" newElem. You created newElem within XMLDocument doc but newElem is just "floating" around as an untracked node until you insert it at a specific location within the XMLDocument. Calling Parse clears the XMLDocument deleting all current nodes and the assert is simply a notification that an untracked node is being deleted.

Call one of the XMLNode::Insert... methods to add elements to the document in the appropriate place. And, in your case, move the call to Parse to create the document element (<TAGS>) before creating child elements.

E.g.

#include "tinyxml2.h"

using namespace tinyxml2;

int main(int argc, char* argv[])
{
    XMLDocument doc;
    doc.Parse("<TAGS></TAGS>");

    XMLElement* newElm = doc.NewElement("Hello");
    newElm->SetText("World");

    doc.InsertEndChild(newElem);

    return 0;
}

My tinyxml2 extension offers a convenient helper function (append_element) to create and insert an element in a single operation.