11.5.2.c

#include <pthread.h>
#include "apue.h"

struct foo {
  int a, b, c, d;
};

void printfoo(const char *s, const struct foo *fp) {
  printf("%s", s);
  printf("  structure at 0x%lx\n", (unsigned long)fp);
  printf("  foo.a = %d\n", fp->a);
  printf("  foo.b = %d\n", fp->b);
  printf("  foo.c = %d\n", fp->c);
  printf("  foo.d = %d\n", fp->d);
}

void *thr_fn1(void *arg) {
  struct foo foo = {1, 2, 3, 4};
  printfoo("thread 1:\n", &foo);
  pthread_exit((void *)&foo);
}

void *thr_fn2(void *arg) {
  printf("thread 2: ID is %lu\n", (unsigned long)pthread_self());
  pthread_exit((void *)0);
}

int main() {
  int err;
  pthread_t tid1, tid2;
  struct foo *fp;

  err = pthread_create(&tid1, NULL, thr_fn1, NULL);
  if (err != 0) {
    err_exit(err, "can't create thread 1");
  }
  err = pthread_join(tid1, (void *)&fp);
  if (err != 0) {
    err_exit(err, "can't join whth thread 1");
  }
  sleep(1);
  printf("parent starting second thread\n");
  err = pthread_create(&tid2, NULL, thr_fn2, NULL);
  if (err != 0) {
    err_exit(err, "can't create thread 2");
  }
  sleep(1);
  printfoo("partne:\n", fp);
  exit(0);
}