执行std :: deque-> front（）时'deque iterator not dereferencable`

Question

following piece of code causes an assert "deque iterator not dereferencable" followed by an exception:

if (data[n].stateFlagQueue->empty()) cstate=0;
else
{
   cstate=data[n].stateFlagQueue->front();
   if (data[n].stateFlagQueue->size()>1) data[n].stateFlagQueue->pop();
}

The assert happens with data[n].stateFlagQueue->front() while stateflagQueue has a size of 3, so there are enough data available. The whole code shown above is secured by a mutex, same is true for the code that runs in an own thread and fills stateFlagQueue with data:

if ((data->stateFlagQueue->empty()) || 
    (data->stateFlagQueue->back()!=data->m_response.cstate))
 data->stateFlagQueue->push(data->m_response.cstate);

So...how can it happen this exception still occurs?

Thanks!

Answer 1

好了，解决了，这之间发生了错误的互斥锁解锁，从而导致了此问题。