Subj : Strange behaviour
To   : comp.programming.threads
From : sunglo
Date : Tue Apr 19 2005 11:03 am

I have the following simple code (I know it's ugly, and many things are
missing, like error checks, etc.):

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define THREADS 5

void *threadfunc(void *unused) {
  printf("Bye\n");
  sleep(5);
  pthread_exit (NULL);
}

int main(void) {
  pthread_t tids[THREADS];
  int i;

  for(i = 0; i < THREADS; i++) {

    printf("main creates thread %d\n", i);
    pthread_create (&tids[i], NULL, threadfunc, NULL);
    printf("created: thread %d\n", i);
  }
  pthread_exit (NULL);
}

I'm using linux 2.6 with NPTL. When this code runs, sometimes it
executes all the threads (ie, the messages from main() *AND* those from
the threads are printed, and the process waits about 5 secs. before
terminating), some other times it terminates immediately (only the
messages from main() are printed, and then it terminates). It almost
seems that, under certain conditions, the call to pthread_exit() from
main() terminates the whole process.
I believe that calling pthread_exit() from main() should not terminate
the whole process...unless, perhaps, at the time main() calls
pthread_exit(), no other thread has actually been created, so, being
main() the only thread, pthread_exit() terminates the process? (just a
guess, I hope you have some better explanation).

Thanks for your answers.

.