Greetings!

I'm having a problem with my QThread classes. I based them on the Qt Example Mandlebrot (I'm also doing an long rendering process). I extracted the core mutex and waitCondition syncronization that was in the renderThread into it's own class (which I call InfiniteThread) and then I sub-class this to specialize what task that thread will perform.

Problem is, whenever an instance of InfiniteThread is destroyed and the destructor gets called I get a SIGABRT and the following console output:

pure virtual method called
terminate called without an active exception
The program has unexpectedly finished.
Here's the top of the stack at the time:

Qt Code: 
  1. 0	__semwait_signal					0	0x00007fff87ecdeb6	
  2. 1	_pthread_cond_wait					0	0x00007fff87ed1cd1	
  3. 2	QWaitCondition::wait					0	0x000000010103bfa0	
  4. 3	QThread::wait						0	0x00000001010a419e	
  5. 4	InfiniteThread::~InfiniteThread	infinitethread.cpp	17	0x000000010001022c	
  6. 5	EMSampleThread::~EMSampleThread	emsamplethread.cpp	18	0x000000010000fbfd	
  7. 6	RFViewer::~RFViewer		rfviewer.cpp		50	0x0000000100008a8f	
  8. 7	main				main.cpp		10	0x000000010000602a
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So the SIGABRT seems to be coming from QThread::wait(), which is called in ~InfiniteThread(). Code for InfiniteThread is included below. Note that InfiniteThread::centralTask() is a pure-virtual member that is re-implemented to specialize the thread for a specific task.

Like I mentioned before, InfiniteThread is based entirely on renderthread.cpp in the Mandlebrot example and it does not have this problem. Any help is much appreciated. I'm new to threading but I am pretty comfortable with Qt.

Thanks!
Seth

InfiniteThread.h:
Qt Code: 
  1. #ifndef INFINITETHREAD_H
  2. #define INFINITETHREAD_H
  3.  
  4. #include <QThread>
  5. #include <QMutex>
  6. #include <QWaitCondition>
  7.  
  8. class InfiniteThread : public QThread
  9. {
  10.     Q_OBJECT
  11.  
  12. public:
  13.     explicit InfiniteThread(QObject *parent = 0);
  14.     ~InfiniteThread();
  15.  
  16. signals:
  17.     void reportProgress(int pProg, QString message);
  18.     void taskDone(bool pSuccess);
  19.  
  20. protected:
  21.     void startTask();
  22.     void run();
  23.  
  24.     // Override this in the child class
  25.     virtual bool centralTask() = 0;
  26.  
  27.     QMutex mutex;
  28.     QWaitCondition condition;
  29.     bool restart;
  30.     bool abort;
  31. };
  32.  
  33. #endif // INFINITETHREAD_H
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InfiniteThread.cpp:
Qt Code: 
  1. #include "infinitethread.h"
  2.  
  3. InfiniteThread::InfiniteThread(QObject *parent) :
  4.     QThread(parent)
  5. {    
  6.     restart = false;
  7.     abort = false;
  8. }
  9.  
  10. InfiniteThread::~InfiniteThread()
  11. {
  12.     mutex.lock();
  13.     abort = true;
  14.     condition.wakeOne();
  15.     mutex.unlock();
  16.  
  17.     wait();
  18. }
  19.  
  20. void InfiniteThread::startTask()
  21. {
  22.     QMutexLocker locker(&mutex);
  23.  
  24.     if (!isRunning()) {
  25.         start(LowPriority);
  26.     } else {
  27.         restart = true;
  28.         condition.wakeOne();
  29.     }
  30. }
  31.  
  32. void InfiniteThread::run()
  33. {
  34.     forever {
  35.         // Perform central task
  36.         bool result = centralTask();
  37.         if(!restart) emit taskDone(result);
  38.  
  39.         // Abort thread if requested
  40.         if(abort) return;
  41.  
  42.         // Restart when new central task is given
  43.         mutex.lock();
  44.         if(!restart) condition.wait(&mutex);
  45.         restart = false;
  46.         mutex.unlock();
  47.     }
  48. }
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