#include <pthread.h>                                    /* interfere.c */
#include <stdio.h>
#include <stdlib.h>  /* for strtol   */
#include <string.h>  /* for strerror */
static volatile long int counter = 0;
static long int max;

void * count(void * arg) {           /* main function for thread */
  long int i, reg, * mycounter = arg;
  for(i = 0; i < max; i++) {
    reg = *mycounter;
    reg = reg + 1;
    *mycounter = reg;
  }
  return NULL;
}

int main (int argc, char * argv[]) {
  int error;
  pthread_t tid;
  max = strtol(argv[1], NULL, 10);
  if (error = pthread_create(&tid, NULL, count, &counter))
   fprintf(stderr, "Failed to spawn: %s\n", strerror(error));
  else {
   count( &counter );
   if (error = pthread_join(tid, NULL))
     fprintf(stderr, "Failed to join: %s\n", strerror(error));
   else
     fprintf(stderr, "The final count was  %ld\n", counter);
  }
  return 0;
}