#include <unistd.h>
#include <signal.h>
#include <ucontext.h>
#define HAVE_SETRLIMIT 1
#if HAVE_SETRLIMIT
# include <sys/types.h>
# include <sys/time.h>
# include <sys/resource.h>
#endif

static union
{
  char buffer[SIGSTKSZ];
  long double ld;
  long u;
  void *p;
} alternate_signal_stack;

#if STACK_DIRECTION
# define find_stack_direction(ptr) STACK_DIRECTION
#else
static int
find_stack_direction (char const *addr)
{
  char dummy;
  return (! addr ? find_stack_direction (&dummy)
	   : addr < &dummy ? 1 : -1);
}
#endif

static void
segv_handler (int signo, siginfo_t *info, void *context)
{
  if (0 < info->si_code)
    {
      ucontext_t const *user_context = context;
      char const *stack_min = user_context->uc_stack.ss_sp;
      size_t stack_size = user_context->uc_stack.ss_size;
      char const *faulting_address = info->si_addr;
      size_t s = faulting_address - stack_min;
      size_t page_size = sysconf (_SC_PAGESIZE);
      if (find_stack_direction (0) < 0)
	 s += page_size;
      if (s < stack_size + page_size)
	 _exit (0);
    }

  _exit (1);
}

static int
c_stack_action (void)
{
  stack_t st;
  struct sigaction act;
  int r;

  st.ss_flags = 0;
  st.ss_sp = alternate_signal_stack.buffer;
  st.ss_size = sizeof alternate_signal_stack.buffer;
  r = sigaltstack (&st, 0);
  if (r != 0)
    return r;

  sigemptyset (&act.sa_mask);
  act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
  act.sa_sigaction = segv_handler;
  return sigaction (SIGSEGV, &act, 0);
}

static int
recurse (char *p)
{
  char array[500];
  array[0] = 1;
  return *p + recurse (array);
}

int
main (void)
{
  #if HAVE_SETRLIMIT && defined RLIMIT_STACK
  /* Before starting the endless recursion, try to be friendly
     to the user's machine.  On some Linux 2.2.x systems, there
     is no stack limit for user processes at all.  We don't want
     to kill such systems.  */
  struct rlimit rl;
  rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
  setrlimit (RLIMIT_STACK, &rl);
  #endif

  c_stack_action ();
  return recurse ("\1");
}