h_errno?

[Eli Zaretskii]

In process.c we have:

  #ifndef HAVE_H_ERRNO
  extern int h_errno;
  #endif

There's also a configure-time test for this variable.  But no code
ever references h_errno in process.c, and the only place that it is
used is in sysdep.c:

  #else /* !HAVE_GETADDRINFO */
          struct hostent *hp;
          for (count = 0;; count++)
            {

  #ifdef TRY_AGAIN
              h_errno = 0;
  #endif
              hp = gethostbyname (hostname);
  #ifdef TRY_AGAIN
              if (! (hp == 0 && h_errno == TRY_AGAIN))
  #endif

                break;

              if (count >= 5)
                break;
              Fsleep_for (make_number (1), Qnil);
            }

What is this variable about, and why do we have its declaration in
process.c?  Can we use errno instead of h_errno in sysdep.c?