deque迭代器不是线程池中的dereferencable错误

Question

我使用SDL2的线程库编写了一个线程池，该库使用以下线程函数：

int threadFunc(void * pData)
{
    ThreadData* data = (ThreadData*)pData;
    SDLTaskManager* pool = data->pool;
    Task* task = nullptr;
    while (true)
    {
        SDL_LockMutex(pool->getMutex());
        while (!pool->isRunning() && !pool->hasTasks())
        {
            SDL_CondWait(pool->getCondition(), pool->getMutex());
        }
        if (pool->shuttingDown())
        {
            return 0;
        }
        task = pool->getNextTask(); //SDL_CondWait relocks mutex, so this *should* be thread safe.
        if (task != nullptr)
        {
            pool->notifyThreadWorking(true);
            data->taskCount++;
        }
        else
        {
            pool->stop();
            SDL_UnlockMutex(pool->getMutex());
            continue;
        }
        SDL_UnlockMutex(pool->getMutex());
        task->execute();
        SDL_LockMutex(pool->getMutex());
        pool->notifyThreadWorking(false);
        pool->addCompleteTask(task);
        SDL_UnlockMutex(pool->getMutex());
    }
    return 0;
}

当调用pool-＆gt; getNextTask（）时，我得到调试断言错误“Deque iterator is dereferencable”。我已经通过调用堆栈检查了池维护的deque的内容，发现调用此函数时它肯定不是空的。

功能代码如下：

Task * SDLTaskManager::getNextTask()
{
    Task* t = nullptr;
    if (!mCurrentTasks.empty())
    {   
        t = mCurrentTasks.front();  //this part is causing the error
        mCurrentTasks.pop_front();  //this is a std::deque<Task*>
    }
    return t;
}

deque中包含有效数据，所以我对导致问题的原因感到茫然。