#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>

static void
die (const char *s)
{
  perror (s);
  exit (EXIT_FAILURE);
}

static void
printsigstack (const char *prefix)
{
  stack_t ss;

  if (sigaltstack (NULL, &ss) < 0)
die ("sigaltstack get");
  printf ("%s %p 0x%lx 0x%x\n", prefix, ss.ss_sp, (unsigned long) ss.ss_size,
      (unsigned int) ss.ss_flags);
}

static void *
thread (void *arg)
{
  stack_t ss;

  printsigstack ("thread");
  ss.ss_sp = malloc (SIGSTKSZ);
  if (ss.ss_sp == NULL)
die ("malloc");
  ss.ss_size = SIGSTKSZ;
  ss.ss_flags = 0;
  if (sigaltstack (&ss, NULL) < 0)
die ("sigaltstack set");
  return NULL;
}

int
main ()
{
  pthread_t tid;
  int i;
  stack_t ss;

  printsigstack ("main 1");

  i = pthread_create (&tid, NULL, thread, NULL);
  if (i != 0)
{
  errno = i;
  die ("pthread_create");
}

  i = pthread_join (tid, NULL);
  if (i != 0) {
errno = i;
die ("pthread_join");
  }

  printsigstack ("main 2");

  ss.ss_sp = malloc (SIGSTKSZ);
  if (ss.ss_sp == NULL)
die ("malloc");
  ss.ss_size = SIGSTKSZ;
  ss.ss_flags = 0;
  if (sigaltstack (&ss, NULL) < 0)
die ("sigaltstack set");

  printsigstack ("main 3");

  i = pthread_create (&tid, NULL, thread, NULL);
  if (i != 0)
{
  errno = i;
  die ("pthread_create");
}

  i = pthread_join (tid, NULL);
  if (i != 0) {
errno = i;
die ("pthread_join");
  }

  printsigstack ("main 4");

  return 0;
}