BloombergLP::bdlcc::SingleConsumerQueueImpl::popFront

Remove the element from the front of this queue and load that element into the specified value. If the queue is empty, block until it is not empty. Return 0 on success, and a non-zero value otherwise. Specifically, return e_DISABLED if isPopFrontDisabled(). On failure, value is not changed. Threads blocked due to the queue being empty will return e_DISABLED if disablePopFront is invoked. The behavior is undefined unless the invoker of this method is the single consumer.