fix some warnings around unused variables, dead stores, potentially dereferencing nullptr and calling virtual functions from constructor

include/libtorrent/peer_connection.hpp

@@ -516,9 +516,9 @@ namespace aux {
 		int est_reciprocation_rate() const { return m_est_reciprocation_rate; }
 
 #ifndef TORRENT_DISABLE_LOGGING
-		bool should_log(peer_log_alert::direction_t direction) const override;
+		bool should_log(peer_log_alert::direction_t direction) const override final;
 		void peer_log(peer_log_alert::direction_t direction
-			, char const* event, char const* fmt, ...) const noexcept override TORRENT_FORMAT(4,5);
+			, char const* event, char const* fmt, ...) const noexcept override final TORRENT_FORMAT(4,5);
 		void peer_log(peer_log_alert::direction_t direction
 			, char const* event) const noexcept;
 

src/kademlia/node.cpp

@@ -453,7 +453,7 @@ void node::announce(sha1_hash const& info_hash, int listen_port, announce_flags_
 	}
 #endif
 
-	if (listen_port == 0)
+	if (listen_port == 0 && m_observer != nullptr)
 	{
 		listen_port = m_observer->get_listen_port(
 			flags & announce::ssl_torrent ? aux::transport::ssl : aux::transport::plaintext

src/peer_connection.cpp

@@ -5893,7 +5893,7 @@ namespace libtorrent {
 			if (buffer_size > 0)
 			{
 				span<char> const vec = m_recv_buffer.reserve(buffer_size);
-				std::size_t bytes = m_socket->read_some(
+				std::size_t const bytes = m_socket->read_some(
 					boost::asio::mutable_buffers_1(vec.data(), vec.size()), ec);
 
 				// this is weird. You would imagine read_some() would do this
@@ -5908,14 +5908,14 @@ namespace libtorrent {
 #endif
 
 				TORRENT_ASSERT(bytes > 0 || ec);
-				if (ec == boost::asio::error::would_block || ec == boost::asio::error::try_again)
+				if (ec)
 				{
-					bytes = 0;
-				}
-				else if (ec)
-				{
-					disconnect(ec, operation_t::sock_read);
-					return;
+					if (ec != boost::asio::error::would_block
+						&& ec != boost::asio::error::try_again)
+					{
+						disconnect(ec, operation_t::sock_read);
+						return;
+					}
 				}
 				else
 				{

src/resolve_links.cpp

@@ -84,7 +84,7 @@ void resolve_links::match(std::shared_ptr<const torrent_info> const& ti
 
 		std::int64_t const file_size = fs.file_size(i);
 
-		auto range = m_file_sizes.equal_range(file_size);
+		auto const range = m_file_sizes.equal_range(file_size);
 		for (auto iter = range.first; iter != range.second; ++iter)
 		{
 			TORRENT_ASSERT(iter->second >= file_index_t(0));

src/utp_stream.cpp

@@ -1793,8 +1793,6 @@ bool utp_socket_impl::send_pkt(int const flags)
 		return false;
 	}
 
-	int packet_size = header_size + payload_size;
-
 	packet_ptr p;
 	std::uint8_t* ptr = nullptr;
 	utp_header* h = nullptr;
@@ -1810,6 +1808,7 @@ bool utp_socket_impl::send_pkt(int const flags)
 			m_sm.inc_stats_counter(counters::utp_payload_pkts_out);
 		}
 
+		int const packet_size = header_size + payload_size;
 		p->size = std::uint16_t(packet_size);
 		p->header_size = std::uint16_t(packet_size - payload_size);
 		p->num_transmissions = 0;
@@ -1883,7 +1882,6 @@ bool utp_socket_impl::send_pkt(int const flags)
 			return false;
 		}
 
-		packet_size = p->size;
 		payload_size = p->size - p->header_size;
 	}
 
@@ -2572,7 +2570,7 @@ bool utp_socket_impl::test_socket_state()
 	return false;
 }
 
-void utp_socket_impl::init_mtu(int link_mtu, int utp_mtu)
+void utp_socket_impl::init_mtu(int const link_mtu, int utp_mtu)
 {
 	INVARIANT_CHECK;
 
@@ -2580,9 +2578,8 @@ void utp_socket_impl::init_mtu(int link_mtu, int utp_mtu)
 	{
 		// we can't use larger packets than this since we're
 		// not allocating any more memory for socket buffers
-		int decrease = link_mtu - TORRENT_ETHERNET_MTU;
+		int const decrease = link_mtu - TORRENT_ETHERNET_MTU;
 		utp_mtu -= decrease;
-		link_mtu -= decrease;
 	}
 
 	// set the ceiling to what we found out from the interface

test/test_block_cache.cpp

@@ -433,6 +433,7 @@ void test_iovec()
 	TEST_SETUP;
 
 	ret = bc.allocate_iovec(iov);
+	TEST_EQUAL(ret, 0);
 	bc.free_iovec(iov);
 }
 
@@ -505,6 +506,7 @@ TORRENT_TEST(delete_piece)
 	rj.storage = pm;
 	rj.argument = remove_flags_t{};
 	ret = bc.try_read(&rj, alloc);
+	TEST_EQUAL(ret, -1);
 
 	cached_piece_entry* pe_ = bc.find_piece(pm.get(), piece_index_t(0));
 	bc.mark_for_eviction(pe_, block_cache::disallow_ghost);