c++ - Joining threads before program termination -

i have vector of threads collect during execution of application. avoid nasty behavior, i'm trying ensure every thread completed when main thread exits. tried call std::thread::join on each thread in vector upon termination event, seems stuck if recent thread hasn't finished work , won't stop blocking after should. it's important note thingmaker::creatething reads frames series of video files , writes them 1 video, know thread should finish work in less time length of video clip being created.

std::vector<std::thread> threadlist; while (!done) {     switch (triggerevent)     {         case 'h': // spawn new thread make thing "in background"         {             thingmaker next_thing = new thingmaker();             threadlist.push_back(std::thread(&thingmaker::creatething, next_thing));             next_thing = null;             break;         }         case 't': // terminate application         {             std::vector<std::thread>::iterator threads;             (threads = threadlist.begin(); threads != threadlist.end(); ++threads)                 threads->join();             done = true;             break;         }         default: break;     } } 

if send 't' before recent thread has finished making video clip , finished altogether, threads->join() blocks forever. however, if wait video clips created, application terminates. understanding, should wait thread finish work , let main thread carry on - misunderstanding?

there 2 possibilities:

1. the thread hasn't finished yet. can add logging code or use debugger see whether case.

2. the thread called join holds lock preventing other thread finishing. calling join waits thread finish , cannot safely called unless you're absolutely sure thread calls join holds no locks other thread might need acquire in order finish. (look closely @ call stack leading call join see if posssibility.)