updatePaintNode example causing segmentation fault

[mxyn]

Hello, I'm just trying to get familiar with updatePaintNode() by running sample code.

This code runs fine. I see a red rectangle show up
from this example

QSGNode *Zones::updatePaintNode(QSGNode * oldNode, UpdatePaintNodeData *)
{
QSGSimpleRectNode *n = static_cast<QSGSimpleRectNode *>(oldNode);
    if(!n) {
        n = new QSGSimpleRectNode();
	n->setColor(Qt::red);
    }
    //n->setRect(boundingRect());
    n->setRect(0,0,500,500);
    n->setColor(Qt::red);
    return n;
}

But this code causes a segmentation fault.
from the bezier example

QSGNode *Zones::updatePaintNode(QSGNode * oldNode, UpdatePaintNodeData *)
{
    QSGGeometryNode *root = nullptr;
    QSGGeometry *geometry = nullptr;

    if(!oldNode){
        root = new QSGGeometryNode;
        geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), 3);
        geometry->setDrawingMode(QSGGeometry::DrawLineLoop);
        geometry->setLineWidth(6);
        root->setFlag(QSGNode::OwnsGeometry);

        geometry->vertexDataAsPoint2D()[0].set(0, 0);
    	geometry->vertexDataAsPoint2D()[1].set(0,500);
  	geometry->vertexDataAsPoint2D()[2].set(500,500);


        QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
        material->setColor(Qt::blue);
        root->setMaterial(material);
        root->setFlag(QSGNode::OwnsMaterial);
    }
    else
    {
        root=static_cast<QSGGeometryNode*>(oldNode);
        geometry = root->geometry();
        geometry->allocate(3);
    }
    root->markDirty(QSGNode::DirtyGeometry);
    qDebug("7");

   if(!root)
	qDebug("no root node");
   else
	qDebug("valid root node");
    return root;
}

Here is the qml file that it is related

import QtQuick 2.0
import DrawZones 1.0


Item {
    anchors.fill: parent

    Zones {
        id: zoneOB 
        anchors.fill: parent
        objectName: "zone"
    } //Zone
}

[dheerendra]

You are missing attach the geometry.

root->setGeometry(geometry);

[mxyn]

@dheerendra AH! THANK YOU! @_@