Program: 29021
Project: 29021
Buggy source:
/** 
 * Here an assumption is taken: Parameter: timestamp: The time which the window determines as current time and will act upon, the value of this parameter should be monotonically increasing. from https://docs.wso2.com/display/CEP400/Inbuilt+Windows#InbuiltWindows-externalTime
 */
@Override protected void process(ComplexEventChunk<StreamEvent> streamEventChunk,Processor nextProcessor,StreamEventCloner streamEventCloner){
  if (streamEventChunk.getFirst() == null) {
    return;
  }
  List<ComplexEventChunk<StreamEvent>> complexEventChunks=new ArrayList<ComplexEventChunk<StreamEvent>>();
synchronized (this) {
    initTiming(streamEventChunk.getFirst());
    StreamEvent nextStreamEvent=streamEventChunk.getFirst();
    while (nextStreamEvent != null) {
      StreamEvent currStreamEvent=nextStreamEvent;
      nextStreamEvent=nextStreamEvent.getNext();
      if (currStreamEvent.getType() == ComplexEvent.Type.TIMER) {
        if (lastScheduledTime <= currStreamEvent.getTimestamp()) {
          if (!flushed) {
            flushToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime);
            flushed=true;
          }
 else {
            if (currentEventChunk.getFirst() != null) {
              appendToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime);
            }
          }
          lastScheduledTime=executionPlanContext.getTimestampGenerator().currentTime() + schedulerTimeout;
          scheduler.notifyAt(lastScheduledTime);
        }
        continue;
      }
 else       if (currStreamEvent.getType() != ComplexEvent.Type.CURRENT) {
        continue;
      }
      long currentEventTime=(Long)timestampExpressionExecutor.execute(currStreamEvent);
      if (lastCurrentEventTime < currentEventTime) {
        lastCurrentEventTime=currentEventTime;
      }
      if (currentEventTime < endTime) {
        cloneAppend(streamEventCloner,currStreamEvent);
      }
 else {
        if (flushed) {
          appendToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime);
          flushed=false;
        }
 else {
          flushToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime);
        }
        endTime=findEndTime(lastCurrentEventTime,startTime,timeToKeep);
        cloneAppend(streamEventCloner,currStreamEvent);
        if (schedulerTimeout > 0) {
          lastScheduledTime=executionPlanContext.getTimestampGenerator().currentTime() + schedulerTimeout;
          scheduler.notifyAt(lastScheduledTime);
        }
      }
    }
  }
  for (  ComplexEventChunk<StreamEvent> complexEventChunk : complexEventChunks) {
    nextProcessor.process(complexEventChunk);
  }
}

Fixed version (ground truth):
/** 
 * Here an assumption is taken: Parameter: timestamp: The time which the window determines as current time and will act upon, the value of this parameter should be monotonically increasing. from https://docs.wso2.com/display/CEP400/Inbuilt+Windows#InbuiltWindows-externalTime
 */
@Override protected void process(ComplexEventChunk<StreamEvent> streamEventChunk,Processor nextProcessor,StreamEventCloner streamEventCloner){
  if (streamEventChunk.getFirst() == null) {
    return;
  }
  List<ComplexEventChunk<StreamEvent>> complexEventChunks=new ArrayList<ComplexEventChunk<StreamEvent>>();
synchronized (this) {
    initTiming(streamEventChunk.getFirst());
    StreamEvent nextStreamEvent=streamEventChunk.getFirst();
    while (nextStreamEvent != null) {
      StreamEvent currStreamEvent=nextStreamEvent;
      nextStreamEvent=nextStreamEvent.getNext();
      if (currStreamEvent.getType() == ComplexEvent.Type.TIMER) {
        if (lastScheduledTime <= currStreamEvent.getTimestamp()) {
          if (!flushed) {
            flushToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime,true);
            flushed=true;
          }
 else {
            if (currentEventChunk.getFirst() != null) {
              appendToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime,true);
            }
          }
          lastScheduledTime=executionPlanContext.getTimestampGenerator().currentTime() + schedulerTimeout;
          scheduler.notifyAt(lastScheduledTime);
        }
        continue;
      }
 else       if (currStreamEvent.getType() != ComplexEvent.Type.CURRENT) {
        continue;
      }
      long currentEventTime=(Long)timestampExpressionExecutor.execute(currStreamEvent);
      if (lastCurrentEventTime < currentEventTime) {
        lastCurrentEventTime=currentEventTime;
      }
      if (currentEventTime < endTime) {
        cloneAppend(streamEventCloner,currStreamEvent);
      }
 else {
        if (flushed) {
          appendToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime,false);
          flushed=false;
        }
 else {
          flushToOutputChunk(streamEventCloner,complexEventChunks,lastCurrentEventTime,false);
        }
        endTime=findEndTime(lastCurrentEventTime,startTime,timeToKeep);
        cloneAppend(streamEventCloner,currStreamEvent);
        if (schedulerTimeout > 0) {
          lastScheduledTime=executionPlanContext.getTimestampGenerator().currentTime() + schedulerTimeout;
          scheduler.notifyAt(lastScheduledTime);
        }
      }
    }
  }
  for (  ComplexEventChunk<StreamEvent> complexEventChunk : complexEventChunks) {
    nextProcessor.process(complexEventChunk);
  }
}