Hi, All

I do a testing which use a work thread to access a variable (here is str) which belong to main thread. I found if I add QueuedConnection in connect function ,it will not crash,but without it will crash .

Does anybody know why?

Thanks advance for your help.

Qt Code: 
  1. #ifndef AAA_
  2. #define AAA_
  3. #include <QThread>
  4. #include <QString>
  5. #include <QDebug>
  6.       class myClass : public QThread
  7.       {
  8.         Q_OBJECT
  9.       public:
  10.           myClass ()
  11.           {
  12.               connect(this, 
  13.                           SIGNAL(startSignal()),
  14.                            this, SLOT(onDoComm())); //will crash
  15.                            //,Qt::QueuedConnection); //add this parameter will not
  16.           }
  17.           void run() { exec(); }
  18.           void startComm() {emit startSignal();}
  19.       signals:
  20.         void startSignal();
  21.       public slots:
  22.         void onDoComm()
  23.         {
  24.             static long i=1;
  25.             qDebug()<<str;
  26.             str=QString("%1%2").arg(i++);
  27.             emit startSignal();
  28.         };
  29.       private:
  30.         QString str;
  31.       };
  32.  
  33.  
  34. #endif
  35.  
  36.  
  37.  
  38. #include <iostream>
  39. #include <QApplication>
  40. #include "aaa.h"
  41.  
  42. using namespace std;
  43. int main(int argc ,char *argv[])
  44. {
  45.     QApplication app(argc, argv);
  46.  
  47.     myClass a;
  48.     a.start();
  49.     a.startComm();
  50.     app.exec();
  51. }
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