PVS-Studio warning V547 for ReactOS

typedef UINT_PTR SOCKET;

#define ADNS_SOCKET SOCKET

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

void adns_finish(adns_state ads) {
  ...
  if (ads->tcpsocket >= 0) adns_socket_close(ads->tcpsocket);
  ...
}

This suspicious code was found in ReactOS project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'ads->tcpsocket >= 0' is always true. Unsigned type value is always >= 0. adns setup.c 683

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/