This avoids a warning from gcc (comparison between signed and unsigned integer expressions [-Werror=sign-compare]), under Windows
@@ -84,7 +84,7 @@ tor_natpmp_cleanup(tor_fw_options_t *tor_fw_options, void *backend_state)
/** Use select() to wait until we can read on fd. */
static int
-wait_until_fd_readable(int fd, struct timeval *timeout)
+wait_until_fd_readable(unsigned int fd, struct timeval *timeout)
{
int r;
fd_set fds;