I'm running in an application crash. gdb's complaining about segmentation fault in QObject::thread (this=(incomplete type)). Here's the code where I suspect the problem is coming from:

Qt Code: 
  1. #include <QtDebug>
  2. #include <QtGUI>
  3. #include <QPainter>
  4. #include <QThread>
  5. #include "webcam.h"
  6. #include "capturingthread.h"
  7. #include "imagebuffer.h"
  8. #include "renderingthread.h"
  9.  
  10. WebcamWidget::WebcamWidget(QWidget *parent) : QWidget(parent)
  11. {
  12.     setupUi(this);
  13.  
  14.     pWaitCondition = &waitCondition;
  15.     imageBuffer = new ImageBuffer(pWaitCondition);
  16.     capturingThread = new CapturingThread(imageBuffer);
  17.     renderingThread = new RenderingThread(imageBuffer,pWaitCondition);
  18.  
  19.     qRegisterMetaType<QImage>("QImage&");
  20.     connect(renderingThread, SIGNAL(renderingDone(QImage& )), this, SLOT(updatePixmap(QImage& )));
  21.     connect(startButton, SIGNAL(clicked()), this, SLOT(startThreads()));
  22. }
  23.  
  24. WebcamWidget::~WebcamWidget()
  25. {
  26.     delete imageBuffer;
  27.     delete capturingThread;
  28.     delete renderingThread;
  29. }
  30.  
  31. void WebcamWidget::startThreads()
  32. {
  33.     if (capturingThread->isRunning())//&&renderingThread->isRunning())
  34.     {
  35.         capturingThread->haltCapture();
  36.         renderingThread->haltRendering();
  37.         startButton->setText("Start");
  38.     }
  39.     else
  40.     {
  41.         capturingThread->start();
  42.         renderingThread->start();
  43.         startButton->setText("Stop");
  44.     }
  45. }
  46.  
  47. void WebcamWidget::haltThreads()
  48. {
  49.     capturingThread->haltCapture();
  50.     renderingThread->haltRendering();
  51. }
  52.  
  53. void WebcamWidget::paintEvent(QPaintEvent*)
  54. {
  55.     QPainter painter(this);
  56.     painter.fillRect(rect(), Qt::black);
  57.     if (pixmap.isNull())
  58.     {
  59.         qDebug()<<"W: Pixmap data null.";
  60.         painter.setPen(Qt::black);
  61.         painter.drawText(rect(), Qt::AlignCenter, "No Image Feed");
  62.         return;
  63.     }
  64.     painter.drawPixmap(10,10,pixmap);
  65.     qDebug()<<"Painting successful.";
  66. }
  67.  
  68. void WebcamWidget::updatePixmap(QImage& image)
  69. {
  70.     qDebug()<<"WebcamWidget::updatePixmap() invoked.";
  71.     pixmap = QPixmap::fromImage(image);
  72.     update();
  73. }
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I only used this in this .cpp file and I don't see this anywhere in my spawned threads' codes. Did I not use it right? TIA.