* We better should not use 'strerror' since it can call far too many
   other functions which might fail.  Do it here ourselves.  */
static void
write_strsignal (int fd, int signal)
{
  if (signal < 0 || signal >= _NSIG || _sys_siglist[signal] == NULL)
    {
      char buf[30];
      char *ptr = _itoa_word (signal, &buf[sizeof (buf)], 10, 0);
      WRITE_STRING ("signal ");
      write (fd, buf, &buf[sizeof (buf)] - ptr);
    }
  else
    WRITE_STRING (_sys_siglist[signal]);
}

* This function is called when a segmentation fault is caught.
 The system is in an unstable state now.
 This means especially that malloc() might not work anymore.  */
static void
catch_segfault (int signal, SIGCONTEXT ctx)
{
  int fd, cnt, i;
  void **arr;
  struct sigaction sa;
  uintptr_t pc;

  /* This is the name of the file we are writing to.  If none is given
     or we cannot write to this file write to stderr.  */
  fd = 2;
  if (fname != NULL)
    {
      fd = open (fname, O_TRUNC | O_WRONLY | O_CREAT, 0666);
      if (fd == -1)
    fd = 2;
    }

  WRITE_STRING ("*** ");
  write_strsignal (fd, signal);
  WRITE_STRING ("\n");

#ifdef REGISTER_DUMP
  REGISTER_DUMP;
#endif

  WRITE_STRING ("\nBacktrace:\n");

  * Get the backtrace.  */
  arr = alloca (256 * sizeof (void *));
  cnt = backtrace (arr, 256);

  * Now try to locate the PC from signal context in the backtrace.
     Normally it will be found at arr[2], but it might appear later
     if there were some signal handler wrappers.  Allow a few bytes
     difference to cope with as many arches as possible.  */
  pc = (uintptr_t) GET_PC (ctx);
  for (i = 0; i < cnt; ++i)
    if ((uintptr_t) arr[i] >= pc - 16 && (uintptr_t) arr[i] <= pc + 16)
      break;

  /* If we haven't found it, better dump full backtrace even including
     the signal handler frames instead of not dumping anything.  */
  if (i == cnt)
    i = 0;

  /* Now generate nicely formatted output.  */
  __backtrace_symbols_fd (arr + i, cnt - i, fd);

#ifdef HAVE_PROC_SELF
  /* Now the link map.  */
  int mapfd = open ("/proc/self/maps", O_RDONLY);
  if (mapfd != -1)
    {
      write (fd, "\nMemory map:\n\n", 14);

      char buf[256];
      ssize_t n;

      while ((n = TEMP_FAILURE_RETRY (read (mapfd, buf, sizeof (buf)))) > 0)
    TEMP_FAILURE_RETRY (write (fd, buf, n));

      close (mapfd);
    }
#endif

  /* Pass on the signal (so that a core file is produced).  */
  sa.sa_handler = SIG_DFL;
  sigemptyset (&sa.sa_mask);
  sa.sa_flags = 0;
  sigaction (signal, &sa, NULL);
  raise (signal);
}