pthreads background execution not working correctly

[mgood7123]

//Original source code found at : https://computing.llnl.gov/tutorials/pthreads/samples/join.c

#if CCR_FORCE_LLVM_INTERPRETER
#error "Clang/LLVM interpreter does not support native to script callback function yet. Consider using CPP built-in compiler or turn on 'Use JIT execution' compiler option in app options menu."
#endif

/*****************************************************************************
* FILE: join.c
* DESCRIPTION:
*   This example demonstrates how to "wait" for thread completions by using
*   the Pthread join routine.  Threads are explicitly created in a joinable
*   state for portability reasons. Use of the pthread_exit status argument is
*   also shown. Compare to detached.c
* AUTHOR: 8/98 Blaise Barney
* LAST REVISED:  01/30/09
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <pthread.h>
#include <unistd.h>

//#define foreground
#define background

#define NUM_THREADS 4

void *BusyWork(void *t)
{
	int i;
	long tid;
	double result = 0.0;
	tid = (long)t;
	printf("Thread %ld starting...\n", tid);
	for (i = 0; i < 1000; i++)
	{
		result = result + sin(i) * tan(i);
	}
	unsigned int interval = 1;
	printf("Thread %ld done. Result = %e\n", tid, result);
	for (int i = 30; i >= 0; i-=interval) {
		printf("this is thread %ld, i have %d seconds left untill i stop\n", tid, i);
		sleep(interval);
	}
	printf("Thread %ld is exiting\n", tid);
	pthread_exit((void*)t);
}

int main(int argc, char *argv[])
{
	pthread_t thread[NUM_THREADS];
	pthread_attr_t attr;
	int rc;
	long t;
	void *status;

	/* Initialize and set thread detached attribute */
	pthread_attr_init(&attr);
	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

	for (t = 0; t < NUM_THREADS; t++) {
		printf("Main: creating thread %ld\n", t);
		rc = pthread_create(&thread[t], &attr, BusyWork, (void *)t);
		if (rc) {
			printf("ERROR; return code from pthread_create() is %d\n", rc);
			exit(-1);
		}
	}

	/* Free attribute and wait for the other threads */
	pthread_attr_destroy(&attr);
	for (t = 0; t < NUM_THREADS; t++) {
		#ifdef foreground
		rc = pthread_join(thread[t], &status);
		if (rc) {
			printf("ERROR; return code from pthread_join() is %d\n", rc);
			exit(-1);
		}
		#endif
		printf("Main: completed join with thread %ld having a status of %ld\n", t, (long)status);
	}

	printf("Main: program completed. Exiting.\n");
	pthread_exit(NULL);
}