PVS-Studio warning V547 for samba

struct server_id {
  uint32_t pid;
  uint32_t vnn;
  uint64_t unique_id;
}

struct server_id interpret_pid(const char *pid_string)
{
  struct server_id result;
  ....
  /* Assigning to result.pid may have overflowed
     Map negative pid to -1: i.e. error */
  if (result.pid < 0) {
    result.pid = -1;
  }
  ....
}

This suspicious code was found in samba project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'result.pid < 0' is always false. Unsigned type value is never < 0. util.c 2376

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/