I want to display an error message whenever my independent thread encounters the word "alert1" in a specific .txt file. But I get the above error inside the monitorForAlerts() inside mythread.cpp file. The line expectedly executes if I were to place it inside dialog.cpp. So I guess this is due to non-inheritance of this object. Can you please advise me how to solve this error for the given code?

Here is the code:
dialog.h
Qt Code: 
  1. #ifndef DIALOG_H
  2. #define DIALOG_H
  3.  
  4. #include <QDialog>
  5. #include <QtCore>
  6. #include "mythread.h"
  7. namespace Ui {
  8. class Dialog;
  9. }
  10.  
  11. class Dialog : public QDialog
  12. {
  13.     Q_OBJECT
  14.  
  15. public:
  16.     explicit Dialog(QWidget *parent = 0);
  17.     ~Dialog();
  18.  
  19. public slots:
  20.  
  21. private:
  22.     Ui::Dialog *ui;
  23.  
  24. private slots:
  25.     void on_pushButton_clicked();
  26.     void on_pushButton_2_clicked();
  27. };
  28.  
  29. #endif // DIALOG_H
To copy to clipboard, switch view to plain text mode 

mythread.h
Qt Code: 
  1. #ifndef MYTHREAD_H
  2. #define MYTHREAD_H
  3.  
  4. #include <QThread>
  5. #include <QtCore>
  6. #include <QDebug>
  7. #include <QFile>
  8. #include <Windows.h>
  9. #include <QMessageBox>
  10. #include <QTimer>
  11. #define ALERTS_MESSAGE_STORAGE_PATH "E:\\QT1\\simpleGUIThread2\\simpleGUIThread2\\usbAlert.txt"
  12. #define TIMER_VALUE                      500
  13. class MyThread : public QThread
  14. {
  15.     Q_OBJECT
  16. public:
  17.     explicit MyThread(QObject *parent = 0);
  18.     void run();
  19.     QString name;
  20.     void monitorForAlerts();
  21.     int exec();
  22.  
  23. public slots:
  24.  
  25. signals:
  26.     void testSignal(QString message);
  27.  
  28. public slots:
  29.  
  30. };
  31.  
  32. #endif // MYTHREAD_H
To copy to clipboard, switch view to plain text mode 

dialog.cpp
Qt Code: 
  1. #include "dialog.h"
  2. #include "ui_dialog.h"
  3.  
  4. Dialog::Dialog(QWidget *parent) :
  5.     QDialog(parent),
  6.     ui(new Ui::Dialog)
  7. {
  8.     ui->setupUi(this);
  9. }
  10.  
  11. Dialog::~Dialog()
  12. {
  13.     delete ui;
  14. }
  15.  
  16. void Dialog::on_pushButton_clicked()
  17. {
  18.     ui->label->show();
  19. }
  20.  
  21. void Dialog::on_pushButton_2_clicked()
  22. {
  23.     ui->label->hide();
  24. }
To copy to clipboard, switch view to plain text mode 

mythread.cpp
Qt Code: 
  1. #include "mythread.h"
  2. #include "dialog.h"
  3. MyThread::MyThread(QObject *parent) :
  4.     QThread(parent)
  5. {
  6. }
  7.  
  8. void MyThread::run()
  9. {
  10.     exec();
  11. }
  12.  
  13. int MyThread::exec()
  14. {
  15.     while(1)
  16.     {
  17.         monitorForAlerts();
  18.         emit(testSignal("hello world!!"));
  19.         sleep(1);
  20.     }
  21. }
  22.  
  23. void MyThread::monitorForAlerts()
  24. {
  25.     QString response = ALERTS_MESSAGE_STORAGE_PATH;
  26.     QFile resp(response);
  27.     resp.open(QIODevice::WriteOnly);
  28.     resp.close();
  29.     QFile resp1(response);
  30.     char buf[121];
  31.     char buf1[] = "alert1";
  32.     char buf2[] = "alert2";
  33.  
  34.     resp1.open(QIODevice::ReadOnly);
  35.     while(resp1.size() == 0)
  36.     {
  37.         Sleep(3000);
  38.     }
  39.     qint64 lineLength = resp1.readLine(buf, sizeof(buf));
  40.     resp1.close();
  41.     if(strcmp(buf,buf1) == 0)
  42.     {
  43.         QFile::remove(ALERTS_MESSAGE_STORAGE_PATH);
  44.         qDebug()<<"warning 1!!";
  45.         QMessageBox::critical(this,tr("ERROR"),tr("Large change in illumination.\nPlease re-capture reference image.\n"));
  46.     }
  47.     if(strcmp(buf,buf2) == 0)
  48.     {
  49.         QFile::remove(ALERTS_MESSAGE_STORAGE_PATH);
  50.         qDebug()<<"warning 2!!";
  51.         QMessageBox::critical(this,tr("ERROR"),tr("The camera position has been moved or an object is obscuring its view.\nPlease check the device.\n"));
  52.     }
  53. }
To copy to clipboard, switch view to plain text mode 

main.cpp
Qt Code: 
  1. #include "dialog.h"
  2. #include <QApplication>
  3. #include "mythread.h"
  4. int main(int argc, char *argv[])
  5. {
  6.     QApplication a(argc, argv);
  7.  
  8.     MyThread mThread1;
  9.     mThread1.name = "mThread1";
  10.     mThread1.start();
  11.  
  12.     Dialog w;
  13.     w.show();
  14.  
  15.     return a.exec();
  16. }
To copy to clipboard, switch view to plain text mode