// #define _POSIX_C_SOURCE 199506L

#include <pthread.h>
#include <iostream>

using std::cout;

pthread_mutex_t  mutex_;
pthread_mutex_t* mutex;

int threadNum;

extern "C" {typedef void*(*cprog)(void*);}

void * program (void *v) {
  int status;
  int number;
  // Decide a thread number -- there may be a better way than this!
  status = pthread_mutex_lock(mutex);
  if (status) cout << "pthread_mutex_lock for threadNum returned " 
							<<status<<"\n";
  number = ++threadNum;
  status = pthread_mutex_unlock(mutex);
  if (status) cout << "pthread_mutex_unlock for threadNum returned " 
							<<status<<"\n";

  // output a few messages:
  for (int i=0; i<400; i++) {
   status = pthread_mutex_lock(mutex);
   if (status) cout << "pthread_mutex_lock for thread "  << number 
					<< " returned " <<status<<"\n";
   cout << "Hello from thread " << number << " --- " << i << "\n";
   status = pthread_mutex_unlock(mutex);
   if (status) cout << "pthread_mutex_unlock for thread "  << number 
					<< " returned " <<status<<"\n";
  }
  return 0;
}

int main() {

  int status;

  // Make a mutex:

  mutex = &mutex_;
  pthread_mutexattr_t mattr_;
  pthread_mutexattr_t *mattr = &mattr_;
  status = pthread_mutex_init(mutex, mattr);
  if (status) cout << "pthread_mutex_init returned status = " <<status<<"\n";

  // Make 2 threads:

  threadNum = 0;

  pthread_attr_t attr_; 
  pthread_attr_t *attr = &attr_;

  status = pthread_attr_init(attr);
  if (status) cout << "pthread_attr_init returned status = " <<status<<"\n";
  status = pthread_attr_setstacksize(attr, 8000000);
  if (status) cout << "pthread_attr_setstacksize returned " <<status<<"\n";

  pthread_t threadA_;
  pthread_t *threadA = &threadA_;
  pthread_t threadB_;
  pthread_t *threadB = &threadB_;

  status =  pthread_create(threadA, attr, (cprog) &program, 0);
  if (status) cout << "pthread_create (A) returned status = " <<status<<"\n";
  status =  pthread_create(threadB, attr, (cprog) &program, 0);
  if (status) cout << "pthread_create (B) returned status = " <<status<<"\n";
  
  // Grab mutex:

  status = pthread_mutex_lock(mutex);
  if (status) cout << "pthread_mutex_lock * returned status = " <<status<<"\n";

  cout << "Hello from main!\n";
  
  status = pthread_mutex_unlock(mutex);
  if (status) cout << "pthread_mutex_unlock * returned " <<status<<"\n";

  // Wait for both threads to end:
  void * retval;
  status = pthread_join (threadB_, &retval);
  if (status) cout << "pthread_join(B) returned " <<status<<"\n";
  status = pthread_join (threadA_, &retval);
  if (status) cout << "pthread_join(A) returned " <<status<<"\n";

  cout << "Bye from main!\n";
  return 0;

}