#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <semaphore.h>
#include <pthread.h>
 
static sem_t sem;
 
void *do_work(void *arg) {
  // if something fails
  printf("Something failed!\n");
  exit(1);
}
 
void exit_handler() {
  sem_post(&sem); // wake up main thread
  sem_wait(&sem); // wait for cleanup in main
  sem_destroy(&sem);
}
 
int main() {
  pthread_t worker_thread;
 
  sem_init(&sem, 0, 0);
  atexit(exit_handler);
 
  pthread_create(&worker_thread, NULL, do_work, NULL);
 
  sem_wait(&sem); // block this thread until work is done
 
  // simulate some cleanup
  usleep(1000000);
  printf("This never gets called!\n");
 
  sem_post(&sem);
}
 

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