BloombergLP::bdlcc::MultipriorityQueue::popFront

Remove the least‐recently added item having the most urgent priority (lowest value) from this multi‐priority queue and load its value into the specified item. If this queue is empty, this method blocks the calling thread until an item becomes available. If the optionally specified itemPriority is non‐null, load the priority of the popped item into itemPriority. The behavior is undefined unless item is non‐null. Note this is unaffected by the enabled / disabled state of the queue.