+ char *h_addr_copy = NULL;
+
+#if HAVE_GETADDRINFO
+ {
+ struct addrinfo hint = { 0 };
+ struct addrinfo *res = NULL;
+ hint.ai_flags = AI_CANONNAME;
+ if (getaddrinfo (host, NULL, &hint, &res) == 0)
+ {
+ h_addr_copy = strdup (res->ai_canonname);
+ freeaddrinfo (res);
+ }
+ }
+#elif HAVE_GETHOSTBYNAME
+ {
+ struct hostent *he = gethostbyname (host);
+
+ if (he)
+ {
+# ifdef HAVE_GETHOSTBYADDR
+ char *addr = NULL;
+
+ /* Try and get an ascii version of the numeric host address. */
+ switch (he->h_addrtype)
+ {
+# ifdef HAVE_INET_NTOA
+ case AF_INET:
+ addr = inet_ntoa (*(struct in_addr *) he->h_addr);
+ break;
+# endif /* HAVE_INET_NTOA */
+ }
+
+ if (addr && strcmp (he->h_name, addr) == 0)
+ {
+ /* gethostbyname has returned a string representation of the IP
+ address, for example, "127.0.0.1". So now, look up the host
+ name via the address. Although it may seem reasonable to look
+ up the host name via the address, we must not pass `he->h_addr'
+ directly to gethostbyaddr because on some systems he->h_addr
+ is located in a static library buffer that is reused in the
+ gethostbyaddr call. Make a copy and use that instead. */
+ h_addr_copy = (char *) malloc (he->h_length);
+ if (h_addr_copy == NULL)
+ he = NULL;
+ else
+ {
+ memcpy (h_addr_copy, he->h_addr, he->h_length);
+ he = gethostbyaddr (h_addr_copy, he->h_length, he->h_addrtype);
+ free (h_addr_copy);
+ }
+ }
+# endif /* HAVE_GETHOSTBYADDR */