Not getting desired output

extern "C" int RTinet_lookup( const char * host,RTinet_address *address,RTinet_port port)
{
  struct addrinfo,*res;
  int errcode;
  char addrstr[INET6_ADDRSTRLEN];


  memset (&hints, 0, sizeof (hints));
  hints.ai_family = AF_UNSPEC;  
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_protocol = IPPROTO_TCP;
  hints.ai_flags |= AI_CANONNAME;

  errcode = getaddrinfo (host, NULL , &hints, &res);
  if (errcode != 0)
    {
      INFO("getaddrinfo");
      return -1;
    }
  INFO(STR("Host: %s", host));
  if(res == NULL)
  {
    INFO(STR("NULL VALUE OF RES"));
  }
  else
  {INFO(STR("IN ELSE PART"));
  while (res)
    {
      INFO(STR("Inside while condition with res "));
      switch (res->ai_family)
        {
        case AF_INET:
          inet_ntop(AF_INET, &((str开发者_运维问答uct sockaddr_in *) res->ai_addr)->sin_addr,addrstr, INET_ADDRSTRLEN);
          break;
        case AF_INET6:
          inet_ntop(AF_INET6, &((struct sockaddr_in6 *) res->ai_addr)->sin6_addr ,addrstr, INET6_ADDRSTRLEN);
          break;
        }
      res = res->ai_next;
    }
   }
   INFO(STR("IPv%d address: %s ", res->ai_family == AF_INET6 ? 6 : 4, addrstr));
   return 1;
}

Here I am passing "::1" as the host address, which is a IPV6 form. But in trace I am getting

Host: ::1    
IPv4 address: ::1

Why this is taking IPv4 ??? It should have taken IPv6 as the address family should be AF_INET6 in this case

---

res is pointing to NULL and hence your last print statement is invalid as you assume ai_family != AF_INET6 must be AF_INET.

edit: To explain further here is your code problem in point, with the non-relevant points removed:

while (res)
{
  res = res->ai_next;
}
INFO(STR("IPv%d address: %s ", res->ai_family == AF_INET6 ? 6 : 4, addrstr));

Ask yourself what is the value of res when the while loop as finished.