Thread on Windows

Question

I have a small question about threading in Windows. I have the following code :

main.cpp

int     main(int ac, char **av)
{
  std::vector<Mthread *>    mythread;
  std::list<std::string>    stack;
  DWORD     id = 0;

  stack.push_back("Maison");
  stack.push_back("Femmes");
  stack.push_back("Fetes");
  stack.push_back("Voitures");
  stack.push_back("Nounours");
  while (id != 5)
  {
      mythread.push_back(new Mthread());
      mythread[mythread.size() - 1]->initThread(&stack, id);
      id++;
  }
  id = 0;
  while (id != 5)
  {
      WaitForInputIdle(mythread[id]->getThread(), INFINITE);
      id++;
  }
  return (1);
}

and Mthread.cpp who is creating my Mthread class.

Mthread::Mthread() {}

Mthread::~Mthread() {}

HANDLE      Mthread::getThread(void) const
{
    return (this->thread);
}

bool        Mthread::initThread(std::list<std::string> *list, DWORD ID)
{
    this->save = list;
    this->thread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Mthread::ThreadFunc, (LPVOID)list, 0, &ID);
    if (this->thread == NULL)
    {
        std::cout << "Erreur lors du lancement du thread" << std::endl;
        return (false);
    }
    else
    {
        return (true);
    }
}

void        Mthread::ThreadFunc(LPVOID list)
{
        std::cout << " is launch" << std::endl;
}

The code is working, but I have a small problem : no string is written on the terminal. But, if I change my code to :

bool        Mthread::initThread(std::list<std::string> *list, DWORD ID)
{
    this->save = list;
    this->thread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Mthread::ThreadFunc, (LPVOID)list, 0, &ID);
    if (this->thread == NULL)
    {
        std::cout << "Erreur lors du lancement du thread" << std::endl;
        return (false);
    }
    else
    {
        std::cout << "OK" << std::endl;
        return (true);
    }
}

Well "OK" and "is launch" is written 5 times on the terminal. I don't understand why. When I pass a small string a to cout it seems to be working, but when I don't nothing is written.

Answer 1

Before terminating, your program should wait until the threads have finished their job. On windows, take a look at WaitForMultipleObjects.

Answer 2

short answer: I guess your main() terminates before the threads have a chance to run. add a sleep() or something similar to main.

More complex answer: - threads and main run independently from eachother. You have to wait in your main until you know you can exit main. - your program tends to be unsafe since the vector is accessed by all threads without any synchronisation. Read up on locks, mutexes and semaphores!