PVS-Studio warning V547 for ReactOS

typedef UINT_PTR SOCKET;
#define ADNS_SOCKET SOCKET

struct adns__state {
  ....
  ADNS_SOCKET udpsocket, tcpsocket;
  ....
};

static int init_finish(adns_state ads) {
  ....
  if (ads->udpsocket<0) { r= errno; goto x_free; }
  ....
}

This suspicious code was found in ReactOS project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'ads->udpsocket < 0' is always false. Unsigned type value is never < 0. setup.c 539

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/