fix some warnings

examples/print.cpp

@@ -74,7 +74,7 @@ std::string add_suffix(float val, char const* suffix)
 std::string color(std::string const& s, color_code c)
 {
 	if (c == col_none) return s;
-	if (std::count(s.begin(), s.end(), ' ') == s.size()) return s;
+	if (std::count(s.begin(), s.end(), ' ') == int(s.size())) return s;
 
 	char buf[1024];
 	snprintf(buf, sizeof(buf), "\x1b[3%dm%s\x1b[39m", c, s.c_str());

src/file.cpp

@@ -1788,6 +1788,8 @@ typedef struct _FILE_ALLOCATED_RANGE_BUFFER {
 		TORRENT_ASSERT(is_open());
 
 #if TORRENT_USE_PREADV
+		TORRENT_UNUSED(flags);
+
 		int ret = iov(&::preadv, native_handle(), file_offset, bufs, num_bufs, ec);
 #else
 
@@ -1836,6 +1838,8 @@ typedef struct _FILE_ALLOCATED_RANGE_BUFFER {
 		ec.clear();
 
 #if TORRENT_USE_PREADV
+		TORRENT_UNUSED(flags);
+
 		int ret = iov(&::pwritev, native_handle(), file_offset, bufs, num_bufs, ec);
 #else
 

src/session_impl.cpp

@@ -320,6 +320,8 @@ namespace aux {
 	// be the hex encoded info-hash
 	int servername_callback(SSL *s, int *ad, void *arg)
 	{
+		TORRENT_UNUSED(ad);
+
 		session_impl* ses = (session_impl*)arg;
 		const char* servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
 

src/torrent.cpp

@@ -5845,6 +5845,8 @@ namespace libtorrent
 	std::string password_callback(int length, boost::asio::ssl::context::password_purpose p
 		, std::string pw)
 	{
+		TORRENT_UNUSED(p);
+
 		if (p != boost::asio::ssl::context::for_reading) return "";
 		return pw;
 	}