diff --git a/.travis.yml b/.travis.yml
index 669b8b1c9..12794b2b9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,7 +4,7 @@ dist: trusty
 matrix:
   fast_finish: true
   include:
-    - env: variant=test_debug sonar_scan=1 toolset=gcc
+    - env: variant=test_release sonar_scan=1 toolset=gcc
     - env: variant=test_debug lint=1 tests=1 toolset=gcc-sanitizer
     - env: variant=test_debug sim=1 crypto=openssl toolset=gcc-sanitizer
     - env: variant=test_release coverage=1 tests=1 toolset=gcc-coverage python=1
@@ -155,7 +155,7 @@ script:
     fi'
 
   - 'if [ "$sonar_scan" == "1" ]; then
-       build-wrapper-linux-x86-64 --out-dir bw-output bjam -a -j3 crypto=$crypto asserts=off invariant-checks=off $toolset variant=$variant -l300 &&
+       build-wrapper-linux-x86-64 --out-dir bw-output bjam -a -j3 crypto=$crypto $toolset variant=$variant -l300 &&
        sonar-scanner -D sonar.login=$SONAR_TOKEN;
     fi'
 
diff --git a/include/libtorrent/aux_/session_impl.hpp b/include/libtorrent/aux_/session_impl.hpp
index 7a4920f9e..a884c74cb 100644
--- a/include/libtorrent/aux_/session_impl.hpp
+++ b/include/libtorrent/aux_/session_impl.hpp
@@ -253,7 +253,7 @@ namespace aux {
 			typedef std::unordered_map<sha1_hash, std::shared_ptr<torrent>> torrent_map;
 
 			explicit session_impl(io_service& ios);
-			virtual ~session_impl();
+			~session_impl() override;
 
 			void start_session(settings_pack pack);
 
diff --git a/include/libtorrent/aux_/session_interface.hpp b/include/libtorrent/aux_/session_interface.hpp
index 52533ec2e..f97c41da2 100644
--- a/include/libtorrent/aux_/session_interface.hpp
+++ b/include/libtorrent/aux_/session_interface.hpp
@@ -313,8 +313,7 @@ namespace libtorrent { namespace aux {
 		virtual bool verify_queue_position(torrent const*, int) = 0;
 #endif
 
-	protected:
-		~session_interface() {}
+		virtual ~session_interface() {}
 	};
 }}
 
diff --git a/include/libtorrent/bt_peer_connection.hpp b/include/libtorrent/bt_peer_connection.hpp
index 0616768c6..42edb49d9 100644
--- a/include/libtorrent/bt_peer_connection.hpp
+++ b/include/libtorrent/bt_peer_connection.hpp
@@ -93,7 +93,7 @@ namespace libtorrent {
 		bt_peer_connection(peer_connection_args const& pack
 			, peer_id const& pid);
 
-		virtual void start() override;
+		void start() override;
 
 		enum
 		{
@@ -119,7 +119,7 @@ namespace libtorrent {
 		void switch_recv_crypto(std::shared_ptr<crypto_plugin> crypto);
 #endif
 
-		virtual connection_type type() const override
+		connection_type type() const override
 		{ return connection_type::bittorrent; }
 
 		enum message_type
@@ -174,13 +174,12 @@ namespace libtorrent {
 
 #if !defined(TORRENT_DISABLE_ENCRYPTION) && !defined(TORRENT_DISABLE_EXTENSIONS)
 		// next_barrier, buffers-to-prepend
-		virtual
 		std::tuple<int, span<span<char const>>>
 		hit_send_barrier(span<span<char>> iovec) override;
 #endif
 
-		virtual void get_specific_peer_info(peer_info& p) const override;
-		virtual bool in_handshake() const override;
+		void get_specific_peer_info(peer_info& p) const override;
+		bool in_handshake() const override;
 		bool packet_finished() const { return m_recv_buffer.packet_finished(); }
 
 #ifndef TORRENT_DISABLE_EXTENSIONS
diff --git a/include/libtorrent/buffer.hpp b/include/libtorrent/buffer.hpp
index 36ec2098f..9eb4b3fcc 100644
--- a/include/libtorrent/buffer.hpp
+++ b/include/libtorrent/buffer.hpp
@@ -82,11 +82,11 @@ public:
 		// the actual allocation may be larger than we requested. If so, let the
 		// user take advantage of every single byte
 #if defined __GLIBC__
-		m_size = malloc_usable_size(m_begin);
+		m_size = ::malloc_usable_size(m_begin);
 #elif defined _MSC_VER
-		m_size = _msize(m_begin);
+		m_size = ::_msize(m_begin);
 #elif defined TORRENT_BSD
-		m_size = malloc_size(m_begin);
+		m_size = ::malloc_size(m_begin);
 #else
 		m_size = size;
 #endif
diff --git a/include/libtorrent/disk_io_thread.hpp b/include/libtorrent/disk_io_thread.hpp
index 99883d294..7447106d3 100644
--- a/include/libtorrent/disk_io_thread.hpp
+++ b/include/libtorrent/disk_io_thread.hpp
@@ -392,7 +392,7 @@ namespace aux {
 		{
 			explicit job_queue(disk_io_thread& owner) : m_owner(owner) {}
 
-			virtual void notify_all() override
+			void notify_all() override
 			{
 				m_job_cond.notify_all();
 			}
diff --git a/include/libtorrent/http_seed_connection.hpp b/include/libtorrent/http_seed_connection.hpp
index 8af1ff62a..472b3880c 100644
--- a/include/libtorrent/http_seed_connection.hpp
+++ b/include/libtorrent/http_seed_connection.hpp
@@ -59,22 +59,22 @@ namespace libtorrent {
 		http_seed_connection(peer_connection_args const& pack
 			, web_seed_t& web);
 
-		virtual connection_type type() const override
+		connection_type type() const override
 		{ return connection_type::http_seed; }
 
 		// called from the main loop when this connection has any
 		// work to do.
-		virtual void on_receive(error_code const& error
+		void on_receive(error_code const& error
 			, std::size_t bytes_transferred) override;
 
-		virtual void on_connected() override;
+		void on_connected() override;
 
 		std::string const& url() const override { return m_url; }
 
-		virtual void get_specific_peer_info(peer_info& p) const override;
-		virtual void disconnect(error_code const& ec, operation_t op, int error = 0) override;
+		void get_specific_peer_info(peer_info& p) const override;
+		void disconnect(error_code const& ec, operation_t op, int error = 0) override;
 
-		virtual void write_request(peer_request const& r) override;
+		void write_request(peer_request const& r) override;
 
 	private:
 
diff --git a/include/libtorrent/http_tracker_connection.hpp b/include/libtorrent/http_tracker_connection.hpp
index e8f4b89e1..7cceb3a36 100644
--- a/include/libtorrent/http_tracker_connection.hpp
+++ b/include/libtorrent/http_tracker_connection.hpp
@@ -66,8 +66,8 @@ namespace libtorrent {
 			, tracker_request const& req
 			, std::weak_ptr<request_callback> c);
 
-		void start();
-		void close();
+		void start() override;
+		void close() override;
 
 	private:
 
@@ -82,7 +82,7 @@ namespace libtorrent {
 		void on_response(error_code const& ec, http_parser const& parser
 			, span<char const> data);
 
-		virtual void on_timeout(error_code const&) {}
+		void on_timeout(error_code const&) override {}
 
 		std::shared_ptr<http_connection> m_tracker_connection;
 		address m_tracker_ip;
diff --git a/include/libtorrent/io.hpp b/include/libtorrent/io.hpp
index 8dbc89324..b33af1f9c 100644
--- a/include/libtorrent/io.hpp
+++ b/include/libtorrent/io.hpp
@@ -180,9 +180,7 @@ namespace detail {
 		template <class OutIt>
 		int write_string(std::string const& val, OutIt& out)
 		{
-			for (std::string::const_iterator i = val.begin()
-				, end(val.end()); i != end; ++i)
-				*out++ = *i;
+			for (auto const c : val) *out++ = c;
 			return int(val.length());
 		}
 	}
diff --git a/include/libtorrent/kademlia/direct_request.hpp b/include/libtorrent/kademlia/direct_request.hpp
index dacea41e7..539f80d21 100644
--- a/include/libtorrent/kademlia/direct_request.hpp
+++ b/include/libtorrent/kademlia/direct_request.hpp
@@ -49,7 +49,7 @@ struct direct_traversal : traversal_algorithm
 		, m_cb(cb)
 	{}
 
-	virtual char const* name() const { return "direct_traversal"; }
+	char const* name() const override { return "direct_traversal"; }
 
 	void invoke_cb(msg const& m)
 	{
@@ -72,13 +72,13 @@ struct direct_observer : observer
 		: observer(algo, ep, id)
 	{}
 
-	virtual void reply(msg const& m)
+	void reply(msg const& m) override
 	{
 		flags |= flag_done;
 		static_cast<direct_traversal*>(algorithm())->invoke_cb(m);
 	}
 
-	virtual void timeout()
+	void timeout() override
 	{
 		if (flags & flag_done) return;
 		flags |= flag_done;
diff --git a/include/libtorrent/kademlia/find_data.hpp b/include/libtorrent/kademlia/find_data.hpp
index d62b52b14..62eaa3332 100644
--- a/include/libtorrent/kademlia/find_data.hpp
+++ b/include/libtorrent/kademlia/find_data.hpp
@@ -58,15 +58,15 @@ struct find_data : traversal_algorithm
 
 	void got_write_token(node_id const& n, std::string write_token);
 
-	virtual void start();
+	void start() override;
 
-	virtual char const* name() const;
+	char const* name() const override;
 
 protected:
 
-	virtual void done();
-	virtual observer_ptr new_observer(udp::endpoint const& ep
-		, node_id const& id);
+	void done() override;
+	observer_ptr new_observer(udp::endpoint const& ep
+		, node_id const& id) override;
 
 	nodes_callback m_nodes_callback;
 	std::map<node_id, std::string> m_write_tokens;
@@ -81,7 +81,7 @@ struct find_data_observer : traversal_observer
 		: traversal_observer(algorithm, ep, id)
 	{}
 
-	virtual void reply(msg const&);
+	void reply(msg const&) override;
 };
 
 } } // namespace libtorrent::dht
diff --git a/include/libtorrent/kademlia/get_item.hpp b/include/libtorrent/kademlia/get_item.hpp
index fbffae790..abfd09467 100644
--- a/include/libtorrent/kademlia/get_item.hpp
+++ b/include/libtorrent/kademlia/get_item.hpp
@@ -63,13 +63,13 @@ public:
 		, data_callback const& dcallback
 		, nodes_callback const& ncallback);
 
-	virtual char const* name() const;
+	char const* name() const override;
 
 protected:
-	virtual observer_ptr new_observer(udp::endpoint const& ep
-		, node_id const& id);
-	virtual bool invoke(observer_ptr o);
-	virtual void done();
+	observer_ptr new_observer(udp::endpoint const& ep
+		, node_id const& id) override;
+	bool invoke(observer_ptr o) override;
+	void done() override;
 
 	data_callback m_data_callback;
 	item m_data;
@@ -85,7 +85,7 @@ public:
 		: find_data_observer(algorithm, ep, id)
 	{}
 
-	virtual void reply(msg const&);
+	void reply(msg const&) override;
 };
 
 } } // namespace libtorrent::dht
diff --git a/include/libtorrent/kademlia/get_peers.hpp b/include/libtorrent/kademlia/get_peers.hpp
index d9ca89495..736d1fa23 100644
--- a/include/libtorrent/kademlia/get_peers.hpp
+++ b/include/libtorrent/kademlia/get_peers.hpp
@@ -48,12 +48,12 @@ struct get_peers : find_data
 		, nodes_callback const& ncallback
 		, bool noseeds);
 
-	virtual char const* name() const;
+	char const* name() const override;
 
 protected:
-	virtual bool invoke(observer_ptr o);
-	virtual observer_ptr new_observer(udp::endpoint const& ep
-		, node_id const& id);
+	bool invoke(observer_ptr o) override;
+	observer_ptr new_observer(udp::endpoint const& ep
+		, node_id const& id) override;
 
 	data_callback m_data_callback;
 	bool m_noseeds;
@@ -68,14 +68,14 @@ struct obfuscated_get_peers : get_peers
 		, nodes_callback const& ncallback
 		, bool noseeds);
 
-	virtual char const* name() const;
+	char const* name() const override;
 
 protected:
 
-	virtual observer_ptr new_observer(udp::endpoint const& ep,
-		node_id const& id);
-	virtual bool invoke(observer_ptr o);
-	virtual void done();
+	observer_ptr new_observer(udp::endpoint const& ep,
+		node_id const& id) override;
+	bool invoke(observer_ptr o) override;
+	void done() override;
 private:
 	// when set to false, we no longer obfuscate
 	// the target hash, and send regular get_peers
@@ -90,7 +90,7 @@ struct get_peers_observer : find_data_observer
 		: find_data_observer(algorithm, ep, id)
 	{}
 
-	virtual void reply(msg const&);
+	void reply(msg const&) override;
 #ifndef TORRENT_DISABLE_LOGGING
 private:
 	void log_peers(msg const& m, bdecode_node const& r, int const size) const;
@@ -104,7 +104,7 @@ struct obfuscated_get_peers_observer : traversal_observer
 		, udp::endpoint const& ep, node_id const& id)
 		: traversal_observer(algorithm, ep, id)
 	{}
-	virtual void reply(msg const&);
+	void reply(msg const&) override;
 };
 
 } } // namespace libtorrent::dht
diff --git a/include/libtorrent/kademlia/node.hpp b/include/libtorrent/kademlia/node.hpp
index 58806892a..24c1e154d 100644
--- a/include/libtorrent/kademlia/node.hpp
+++ b/include/libtorrent/kademlia/node.hpp
@@ -73,7 +73,7 @@ public:
 		: observer(algo, ep, id)
 	{}
 
-	void reply(msg const&) { flags |= flag_done; }
+	void reply(msg const&) override { flags |= flag_done; }
 };
 
 struct socket_manager
@@ -87,7 +87,7 @@ protected:
 // get the closest node to the id with the given family_name
 using get_foreign_node_t = std::function<node*(node_id const&, std::string const&)>;
 
-class TORRENT_EXTRA_EXPORT node : boost::noncopyable
+class TORRENT_EXTRA_EXPORT node
 {
 public:
 	node(aux::listen_socket_handle const& sock, socket_manager* sock_man
@@ -99,6 +99,9 @@ public:
 
 	~node();
 
+	node(node const&) = delete;
+	node& operator=(node const&) = delete;
+
 	void update_node_id();
 
 	void tick();
diff --git a/include/libtorrent/kademlia/put_data.hpp b/include/libtorrent/kademlia/put_data.hpp
index 88657a4b5..f46fe8149 100644
--- a/include/libtorrent/kademlia/put_data.hpp
+++ b/include/libtorrent/kademlia/put_data.hpp
@@ -51,8 +51,8 @@ struct put_data: traversal_algorithm
 
 	put_data(node& node, put_callback const& callback);
 
-	virtual char const* name() const override;
-	virtual void start() override;
+	char const* name() const override;
+	void start() override;
 
 	void set_data(item const& data) { m_data = data; }
 
@@ -60,8 +60,8 @@ struct put_data: traversal_algorithm
 
 protected:
 
-	virtual void done() override;
-	virtual bool invoke(observer_ptr o) override;
+	void done() override;
+	bool invoke(observer_ptr o) override;
 
 	put_callback m_put_callback;
 	item m_data;
@@ -78,7 +78,7 @@ struct put_data_observer : traversal_observer
 	{
 	}
 
-	virtual void reply(msg const&) { done(); }
+	void reply(msg const&) override { done(); }
 
 	std::string m_token;
 };
diff --git a/include/libtorrent/kademlia/refresh.hpp b/include/libtorrent/kademlia/refresh.hpp
index 318ccd9b5..5a8893fd3 100644
--- a/include/libtorrent/kademlia/refresh.hpp
+++ b/include/libtorrent/kademlia/refresh.hpp
@@ -45,16 +45,16 @@ public:
 
 	bootstrap(node& dht_node, node_id const& target
 		, done_callback const& callback);
-	virtual char const* name() const;
+	char const* name() const override;
 
 	observer_ptr new_observer(udp::endpoint const& ep
-		, node_id const& id);
+		, node_id const& id) override;
 
 protected:
 
-	virtual bool invoke(observer_ptr o);
+	bool invoke(observer_ptr o) override;
 
-	virtual void done();
+	void done() override;
 
 };
 
diff --git a/include/libtorrent/kademlia/rpc_manager.hpp b/include/libtorrent/kademlia/rpc_manager.hpp
index b09577fd7..912194bda 100644
--- a/include/libtorrent/kademlia/rpc_manager.hpp
+++ b/include/libtorrent/kademlia/rpc_manager.hpp
@@ -55,11 +55,11 @@ struct dht_settings;
 struct dht_logger;
 struct socket_manager;
 
-struct TORRENT_EXTRA_EXPORT null_observer : public observer
+struct TORRENT_EXTRA_EXPORT null_observer : observer
 {
 	null_observer(std::shared_ptr<traversal_algorithm> const& a
 		, udp::endpoint const& ep, node_id const& id): observer(a, ep, id) {}
-	virtual void reply(msg const&) { flags |= flag_done; }
+	void reply(msg const&) override { flags |= flag_done; }
 };
 
 class routing_table;
diff --git a/include/libtorrent/kademlia/sample_infohashes.hpp b/include/libtorrent/kademlia/sample_infohashes.hpp
index 5a3f7a1ca..c91adb673 100644
--- a/include/libtorrent/kademlia/sample_infohashes.hpp
+++ b/include/libtorrent/kademlia/sample_infohashes.hpp
@@ -53,7 +53,7 @@ public:
 		, node_id const& target
 		, data_callback const& dcallback);
 
-	virtual char const* name() const override;
+	char const* name() const override;
 
 	void got_samples(time_duration interval
 		, int num, std::vector<sha1_hash> samples
@@ -71,7 +71,7 @@ public:
 	sample_infohashes_observer(std::shared_ptr<traversal_algorithm> const& algorithm
 		, udp::endpoint const& ep, node_id const& id);
 
-	virtual void reply(msg const&) override;
+	void reply(msg const&) override;
 };
 
 }} // namespace libtorrent::dht
diff --git a/include/libtorrent/kademlia/traversal_algorithm.hpp b/include/libtorrent/kademlia/traversal_algorithm.hpp
index 73ee5df78..00a32213f 100644
--- a/include/libtorrent/kademlia/traversal_algorithm.hpp
+++ b/include/libtorrent/kademlia/traversal_algorithm.hpp
@@ -162,7 +162,7 @@ struct traversal_observer : observer
 	{}
 
 	// parses out "nodes" and keeps traversing
-	virtual void reply(msg const&);
+	void reply(msg const&) override;
 };
 
 } // namespace dht
diff --git a/include/libtorrent/natpmp.hpp b/include/libtorrent/natpmp.hpp
index a0d9ccbb1..1cb204501 100644
--- a/include/libtorrent/natpmp.hpp
+++ b/include/libtorrent/natpmp.hpp
@@ -79,7 +79,7 @@ private:
 
 	void disable(error_code const& ec);
 
-	struct mapping_t : public aux::base_mapping
+	struct mapping_t : aux::base_mapping
 	{
 		// the local port for this mapping. If this is set
 		// to 0, the mapping is not in use
diff --git a/include/libtorrent/packet_pool.hpp b/include/libtorrent/packet_pool.hpp
index b0556397a..648802152 100644
--- a/include/libtorrent/packet_pool.hpp
+++ b/include/libtorrent/packet_pool.hpp
@@ -88,9 +88,9 @@ namespace libtorrent {
 		// sent with the DF bit set (Don't Fragment)
 		bool mtu_probe:1;
 
-	#if TORRENT_USE_ASSERTS
+#if TORRENT_USE_ASSERTS
 		int num_fast_resend;
-	#endif
+#endif
 
 		// the actual packet buffer
 		std::uint8_t buf[1];
diff --git a/include/libtorrent/pe_crypto.hpp b/include/libtorrent/pe_crypto.hpp
index ea898e217..70f51e410 100644
--- a/include/libtorrent/pe_crypto.hpp
+++ b/include/libtorrent/pe_crypto.hpp
@@ -63,7 +63,8 @@ namespace libtorrent {
 
 	// RC4 state from libtomcrypt
 	struct rc4 {
-		int x, y;
+		int x;
+		int y;
 		aux::array<std::uint8_t, 256> buf;
 	};
 
@@ -88,9 +89,6 @@ namespace libtorrent {
 
 	private:
 
-		int get_local_key_size() const
-		{ return sizeof(m_dh_local_key); }
-
 		key_t m_dh_local_key;
 		key_t m_dh_local_secret;
 		key_t m_dh_shared_secret;
diff --git a/include/libtorrent/peer_connection.hpp b/include/libtorrent/peer_connection.hpp
index 90310db88..50e89fba3 100644
--- a/include/libtorrent/peer_connection.hpp
+++ b/include/libtorrent/peer_connection.hpp
@@ -278,7 +278,7 @@ namespace aux {
 		// do in the constructor).
 		virtual void start();
 
-		virtual ~peer_connection() override;
+		~peer_connection() override;
 
 		void set_peer_info(torrent_peer* pi) override
 		{
@@ -653,7 +653,7 @@ namespace aux {
 #endif
 
 		time_t last_seen_complete() const { return m_last_seen_complete; }
-		void set_last_seen_complete(int ago) { m_last_seen_complete = time(0) - ago; }
+		void set_last_seen_complete(int ago) { m_last_seen_complete = ::time(0) - ago; }
 
 		std::int64_t uploaded_in_last_round() const
 		{ return m_statistics.total_payload_upload() - m_uploaded_at_last_round; }
diff --git a/include/libtorrent/peer_connection_handle.hpp b/include/libtorrent/peer_connection_handle.hpp
index 8337b2cf3..438aa7ddd 100644
--- a/include/libtorrent/peer_connection_handle.hpp
+++ b/include/libtorrent/peer_connection_handle.hpp
@@ -130,7 +130,7 @@ private:
 	}
 };
 
-struct TORRENT_EXPORT bt_peer_connection_handle : public peer_connection_handle
+struct TORRENT_EXPORT bt_peer_connection_handle : peer_connection_handle
 {
 	explicit bt_peer_connection_handle(peer_connection_handle pc)
 		: peer_connection_handle(pc)
diff --git a/include/libtorrent/resolver.hpp b/include/libtorrent/resolver.hpp
index 8841e555b..e3868230d 100644
--- a/include/libtorrent/resolver.hpp
+++ b/include/libtorrent/resolver.hpp
@@ -52,12 +52,12 @@ struct TORRENT_EXTRA_EXPORT resolver final : resolver_interface
 {
 	explicit resolver(io_service& ios);
 
-	virtual void async_resolve(std::string const& host, resolver_flags flags
+	void async_resolve(std::string const& host, resolver_flags flags
 		, callback_t const& h) override;
 
-	virtual void abort() override;
+	void abort() override;
 
-	virtual void set_cache_timeout(seconds timeout) override;
+	void set_cache_timeout(seconds timeout) override;
 
 private:
 
diff --git a/include/libtorrent/sha512.hpp b/include/libtorrent/sha512.hpp
index 09461d5f8..fac3eeadf 100644
--- a/include/libtorrent/sha512.hpp
+++ b/include/libtorrent/sha512.hpp
@@ -8,7 +8,8 @@ namespace libtorrent {
 
 	struct sha512_ctx
 	{
-		std::uint64_t length, state[8];
+		std::uint64_t length;
+		std::uint64_t state[8];
 		std::size_t curlen;
 		std::uint8_t buf[128];
 	};
diff --git a/include/libtorrent/storage.hpp b/include/libtorrent/storage.hpp
index 6a9f144d9..8f2f34ea6 100644
--- a/include/libtorrent/storage.hpp
+++ b/include/libtorrent/storage.hpp
@@ -73,9 +73,9 @@ POSSIBILITY OF SUCH DAMAGE.
 //	struct temp_storage : storage_interface
 //	{
 //		temp_storage(file_storage const& fs) : storage_interface(fs) {}
-//		virtual bool initialize(storage_error& se) { return false; }
-//		virtual bool has_any_file() { return false; }
-//		virtual int read(char* buf, int piece, int offset, int size)
+//		bool initialize(storage_error& se) override { return false; }
+//		bool has_any_file() override { return false; }
+//		int read(char* buf, int piece, int offset, int size) override
 //		{
 //			std::map<int, std::vector<char>>::const_iterator i = m_file_data.find(piece);
 //			if (i == m_file_data.end()) return 0;
@@ -85,22 +85,22 @@ POSSIBILITY OF SUCH DAMAGE.
 //			memcpy(buf, &i->second[offset], available);
 //			return available;
 //		}
-//		virtual int write(const char* buf, int piece, int offset, int size)
+//		int write(const char* buf, int piece, int offset, int size) override
 //		{
 //			std::vector<char>& data = m_file_data[piece];
 //			if (data.size() < offset + size) data.resize(offset + size);
 //			std::memcpy(&data[offset], buf, size);
 //			return size;
 //		}
-//		virtual bool rename_file(file_index_t file, std::string const& new_name)
+//		bool rename_file(file_index_t file, std::string const& new_name) override
 //		{ assert(false); return false; }
-//		virtual status_t move_storage(std::string const& save_path) { return false; }
-//		virtual bool verify_resume_data(add_torrent_params const& rd
+//		status_t move_storage(std::string const& save_path) override { return false; }
+//		bool verify_resume_data(add_torrent_params const& rd
 //			, std::vector<std::string> const* links
-//			, storage_error& error) { return false; }
-//		virtual std::int64_t physical_offset(int piece, int offset)
+//			, storage_error& error) override { return false; }
+//		std::int64_t physical_offset(int piece, int offset) override
 //		{ return piece * files().piece_length() + offset; };
-//		virtual sha1_hash hash_for_slot(int piece, partial_hash& ph, int piece_size)
+//		sha1_hash hash_for_slot(int piece, partial_hash& ph, int piece_size) override
 //		{
 //			int left = piece_size - ph.offset;
 //			assert(left >= 0);
@@ -116,8 +116,8 @@ POSSIBILITY OF SUCH DAMAGE.
 //			}
 //			return ph.h.final();
 //		}
-//		virtual bool release_files() { return false; }
-//		virtual bool delete_files() { return false; }
+//		bool release_files() override { return false; }
+//		bool delete_files() override { return false; }
 //
 //		std::map<int, std::vector<char>> m_file_data;
 //	};
@@ -161,13 +161,15 @@ namespace libtorrent {
 	// reads garbage. It's useful mostly for benchmarking and profiling purpose.
 	//
 	struct TORRENT_EXPORT storage_interface
-		: public std::enable_shared_from_this<storage_interface>
-		, public aux::disk_job_fence
-		, public aux::storage_piece_set
-		, boost::noncopyable
+		: std::enable_shared_from_this<storage_interface>
+		, aux::disk_job_fence
+		, aux::storage_piece_set
 	{
 		explicit storage_interface(file_storage const& fs) : m_files(fs) {}
 
+		storage_interface(storage_interface const&) = delete;
+		storage_interface& operator=(storage_interface const&) = delete;
+
 		// This function is called when the storage is to be initialized. The
 		// default storage will create directories and empty files at this point.
 		// If ``allocate_files`` is true, it will also ``ftruncate`` all files to
@@ -283,7 +285,7 @@ namespace libtorrent {
 		//
 		// .. code:: c++
 		//
-		//		struct disk_buffer_pool : boost::noncopyable
+		//		struct disk_buffer_pool
 		//		{
 		//			char* allocate_buffer(char const* category);
 		//			void free_buffer(char* buf);
@@ -380,20 +382,20 @@ namespace libtorrent {
 		// hidden
 		~default_storage() override;
 
-		virtual bool has_any_file(storage_error& ec) override;
-		virtual void set_file_priority(aux::vector<std::uint8_t, file_index_t> const& prio
+		bool has_any_file(storage_error& ec) override;
+		void set_file_priority(aux::vector<std::uint8_t, file_index_t> const& prio
 			, storage_error& ec) override;
-		virtual void rename_file(file_index_t index, std::string const& new_filename
+		void rename_file(file_index_t index, std::string const& new_filename
 			, storage_error& ec) override;
-		virtual void release_files(storage_error& ec) override;
-		virtual void delete_files(remove_flags_t options, storage_error& ec) override;
-		virtual void initialize(storage_error& ec) override;
-		virtual status_t move_storage(std::string const& save_path
+		void release_files(storage_error& ec) override;
+		void delete_files(remove_flags_t options, storage_error& ec) override;
+		void initialize(storage_error& ec) override;
+		status_t move_storage(std::string const& save_path
 			, move_flags_t flags, storage_error& ec) override;
-		virtual bool verify_resume_data(add_torrent_params const& rd
+		bool verify_resume_data(add_torrent_params const& rd
 			, aux::vector<std::string, file_index_t> const& links
 			, storage_error& error) override;
-		virtual bool tick() override;
+		bool tick() override;
 
 		int readv(span<iovec_t const> bufs
 			, piece_index_t piece, int offset, open_mode_t flags, storage_error& ec) override;
diff --git a/include/libtorrent/torrent.hpp b/include/libtorrent/torrent.hpp
index 89c687de2..b1a4326e6 100644
--- a/include/libtorrent/torrent.hpp
+++ b/include/libtorrent/torrent.hpp
@@ -700,17 +700,17 @@ namespace libtorrent {
 		// (either http_tracker_connection or udp_tracker_connection)
 		// when this torrent got a response from its tracker request
 		// or when a failure occurred
-		virtual void tracker_response(
+		void tracker_response(
 			tracker_request const& r
 			, address const& tracker_ip
 			, std::list<address> const& ip_list
 			, struct tracker_response const& resp) override;
-		virtual void tracker_request_error(tracker_request const& r
+		void tracker_request_error(tracker_request const& r
 			, int response_code, error_code const& ec, const std::string& msg
 			, seconds32 retry_interval) override;
-		virtual void tracker_warning(tracker_request const& req
+		void tracker_warning(tracker_request const& req
 			, std::string const& msg) override;
-		virtual void tracker_scrape_response(tracker_request const& req
+		void tracker_scrape_response(tracker_request const& req
 			, int complete, int incomplete, int downloaded, int downloaders) override;
 
 		void update_scrape_state();
@@ -995,8 +995,8 @@ namespace libtorrent {
 
 		void write_resume_data(add_torrent_params& atp) const;
 
-		void seen_complete() { m_last_seen_complete = time(0); }
-		int time_since_complete() const { return int(time(0) - m_last_seen_complete); }
+		void seen_complete() { m_last_seen_complete = ::time(0); }
+		int time_since_complete() const { return int(::time(0) - m_last_seen_complete); }
 		time_t last_seen_complete() const { return m_last_seen_complete; }
 
 		template <typename Fun, typename... Args>
@@ -1004,8 +1004,8 @@ namespace libtorrent {
 
 		// LOGGING
 #ifndef TORRENT_DISABLE_LOGGING
-		virtual bool should_log() const override;
-		virtual void debug_log(const char* fmt, ...) const override TORRENT_FORMAT(2,3);
+		bool should_log() const override;
+		void debug_log(const char* fmt, ...) const override TORRENT_FORMAT(2,3);
 
 		void log_to_all_peers(char const* message);
 		time_point m_dht_start_time;
diff --git a/include/libtorrent/torrent_peer_allocator.hpp b/include/libtorrent/torrent_peer_allocator.hpp
index c548e7b08..fcf99a253 100644
--- a/include/libtorrent/torrent_peer_allocator.hpp
+++ b/include/libtorrent/torrent_peer_allocator.hpp
@@ -64,8 +64,8 @@ namespace libtorrent {
 	{
 		torrent_peer_allocator();
 
-		torrent_peer* allocate_peer_entry(int type);
-		void free_peer_entry(torrent_peer* p);
+		torrent_peer* allocate_peer_entry(int type) override;
+		void free_peer_entry(torrent_peer* p) override;
 
 		std::uint64_t total_bytes() const { return m_total_bytes; }
 		std::uint64_t total_allocations() const { return m_total_allocations; }
diff --git a/include/libtorrent/tracker_manager.hpp b/include/libtorrent/tracker_manager.hpp
index b382d9a21..042c66876 100644
--- a/include/libtorrent/tracker_manager.hpp
+++ b/include/libtorrent/tracker_manager.hpp
@@ -253,10 +253,12 @@ namespace libtorrent {
 
 	struct TORRENT_EXTRA_EXPORT timeout_handler
 		: std::enable_shared_from_this<timeout_handler>
-		, boost::noncopyable
 	{
 		explicit timeout_handler(io_service& str);
 
+		timeout_handler(timeout_handler const&) = delete;
+		timeout_handler& operator=(timeout_handler const&) = delete;
+
 		void set_timeout(int completion_timeout, int read_timeout);
 		void restart_read_timeout();
 		void cancel();
@@ -300,7 +302,7 @@ namespace libtorrent {
 			, std::weak_ptr<request_callback> r);
 
 		std::shared_ptr<request_callback> requester() const;
-		virtual ~tracker_connection() {}
+		~tracker_connection() override {}
 
 		tracker_request const& tracker_req() const { return m_req; }
 
@@ -334,8 +336,7 @@ namespace libtorrent {
 	};
 
 	class TORRENT_EXTRA_EXPORT tracker_manager final
-		: boost::noncopyable
-		, single_threaded
+		: single_threaded
 	{
 	public:
 
@@ -357,7 +358,11 @@ namespace libtorrent {
 			, aux::session_logger& ses
 #endif
 			);
-		virtual ~tracker_manager();
+
+		~tracker_manager();
+
+		tracker_manager(tracker_manager const&) = delete;
+		tracker_manager& operator=(tracker_manager const&) = delete;
 
 		void queue_request(
 			io_service& ios
diff --git a/include/libtorrent/udp_tracker_connection.hpp b/include/libtorrent/udp_tracker_connection.hpp
index 4bdf68dc4..5feab1fc1 100644
--- a/include/libtorrent/udp_tracker_connection.hpp
+++ b/include/libtorrent/udp_tracker_connection.hpp
@@ -59,8 +59,8 @@ namespace libtorrent {
 			, tracker_request const& req
 			, std::weak_ptr<request_callback> c);
 
-		void start();
-		void close();
+		void start() override;
+		void close() override;
 
 		std::uint32_t transaction_id() const { return m_transaction_id; }
 
@@ -103,7 +103,7 @@ namespace libtorrent {
 		void send_udp_announce();
 		void send_udp_scrape();
 
-		virtual void on_timeout(error_code const& ec);
+		void on_timeout(error_code const& ec) override;
 
 		udp::endpoint pick_target_endpoint() const;
 
diff --git a/include/libtorrent/upnp.hpp b/include/libtorrent/upnp.hpp
index 2dce71a88..f77286c30 100644
--- a/include/libtorrent/upnp.hpp
+++ b/include/libtorrent/upnp.hpp
@@ -246,7 +246,7 @@ private:
 		tcp::endpoint local_ep;
 	};
 
-	struct mapping_t : public aux::base_mapping
+	struct mapping_t : aux::base_mapping
 	{
 		// the local port for this mapping. If this is set
 		// to 0, the mapping is not in use
diff --git a/include/libtorrent/web_connection_base.hpp b/include/libtorrent/web_connection_base.hpp
index 175de072f..ff3f966dc 100644
--- a/include/libtorrent/web_connection_base.hpp
+++ b/include/libtorrent/web_connection_base.hpp
@@ -61,44 +61,44 @@ namespace libtorrent {
 		web_connection_base(peer_connection_args const& pack
 			, web_seed_t& web);
 
-		virtual int timeout() const;
-		void start();
+		int timeout() const override;
+		void start() override;
 
-		~web_connection_base();
+		~web_connection_base() override;
 
 		// called from the main loop when this connection has any
 		// work to do.
 		void on_sent(error_code const& error
-			, std::size_t bytes_transferred);
+			, std::size_t bytes_transferred) override;
 
 		virtual std::string const& url() const = 0;
 
-		bool in_handshake() const;
+		bool in_handshake() const override;
 
 		// the following functions appends messages
 		// to the send buffer
-		void write_choke() {}
-		void write_unchoke() {}
-		void write_interested() {}
-		void write_not_interested() {}
-		virtual void write_request(peer_request const&) = 0;
-		void write_cancel(peer_request const&) {}
-		void write_have(piece_index_t) {}
-		void write_dont_have(piece_index_t) {}
-		void write_piece(peer_request const&, disk_buffer_holder)
+		void write_choke() override {}
+		void write_unchoke() override {}
+		void write_interested() override {}
+		void write_not_interested() override {}
+		void write_request(peer_request const&) override = 0;
+		void write_cancel(peer_request const&) override {}
+		void write_have(piece_index_t) override {}
+		void write_dont_have(piece_index_t) override {}
+		void write_piece(peer_request const&, disk_buffer_holder) override
 		{ TORRENT_ASSERT_FAIL(); }
-		void write_keepalive() {}
-		void on_connected();
-		void write_reject_request(peer_request const&) {}
-		void write_allow_fast(piece_index_t) {}
-		void write_suggest(piece_index_t) {}
-		void write_bitfield() {}
+		void write_keepalive() override {}
+		void on_connected() override;
+		void write_reject_request(peer_request const&) override {}
+		void write_allow_fast(piece_index_t) override {}
+		void write_suggest(piece_index_t) override {}
+		void write_bitfield() override {}
 
 #if TORRENT_USE_INVARIANT_CHECKS
 		void check_invariant() const;
 #endif
 
-		virtual void get_specific_peer_info(peer_info& p) const;
+		void get_specific_peer_info(peer_info& p) const override;
 
 	protected:
 
diff --git a/include/libtorrent/web_peer_connection.hpp b/include/libtorrent/web_peer_connection.hpp
index b5129c9c3..0eeaf1597 100644
--- a/include/libtorrent/web_peer_connection.hpp
+++ b/include/libtorrent/web_peer_connection.hpp
@@ -60,25 +60,25 @@ namespace libtorrent {
 		web_peer_connection(peer_connection_args const& pack
 			, web_seed_t& web);
 
-		virtual void on_connected() override;
+		void on_connected() override;
 
-		virtual connection_type type() const override
+		connection_type type() const override
 		{ return connection_type::url_seed; }
 
 		// called from the main loop when this connection has any
 		// work to do.
-		virtual void on_receive(error_code const& error
+		void on_receive(error_code const& error
 			, std::size_t bytes_transferred) override;
 
 		std::string const& url() const override { return m_url; }
 
-		virtual void get_specific_peer_info(peer_info& p) const override;
-		virtual void disconnect(error_code const& ec
+		void get_specific_peer_info(peer_info& p) const override;
+		void disconnect(error_code const& ec
 			, operation_t op, int error = 0) override;
 
-		virtual void write_request(peer_request const& r) override;
+		void write_request(peer_request const& r) override;
 
-		virtual bool received_invalid_data(piece_index_t index, bool single_peer) override;
+		bool received_invalid_data(piece_index_t index, bool single_peer) override;
 
 	private:
 
diff --git a/src/alert.cpp b/src/alert.cpp
index 7e7d9dcdc..e2fb28c34 100644
--- a/src/alert.cpp
+++ b/src/alert.cpp
@@ -812,11 +812,11 @@ namespace {
 		return type_str[sock_type_idx(type)];
 	}
 
-	static char const* const nat_type_str[] = {"NAT-PMP", "UPnP"};
+	char const* const nat_type_str[] = {"NAT-PMP", "UPnP"};
 
-	static char const* const protocol_str[] = {"none", "TCP", "UDP"};
+	char const* const protocol_str[] = {"none", "TCP", "UDP"};
 
-	static char const* const socket_type_str[] = {
+	char const* const socket_type_str[] = {
 		"null",
 		"TCP",
 		"Socks5/TCP",
diff --git a/src/allocator.cpp b/src/allocator.cpp
index c53c43b8e..a4f5f1166 100644
--- a/src/allocator.cpp
+++ b/src/allocator.cpp
@@ -88,7 +88,7 @@ namespace libtorrent {
 #elif defined TORRENT_BEOS
 		s = B_PAGE_SIZE;
 #else
-		s = int(sysconf(_SC_PAGESIZE));
+		s = int(::sysconf(_SC_PAGESIZE));
 #endif
 		// assume the page size is 4 kiB if we
 		// fail to query it
@@ -113,12 +113,12 @@ namespace libtorrent {
 
 		void* ret;
 #if TORRENT_USE_POSIX_MEMALIGN
-		if (posix_memalign(&ret, std::size_t(page_size()), std::size_t(bytes))
+		if (::posix_memalign(&ret, std::size_t(page_size()), std::size_t(bytes))
 			!= 0) ret = nullptr;
 #elif TORRENT_USE_MEMALIGN
-		ret = memalign(std::size_t(page_size()), std::size_t(bytes));
+		ret = ::memalign(std::size_t(page_size()), std::size_t(bytes));
 #elif defined TORRENT_WINDOWS
-		ret = _aligned_malloc(std::size_t(bytes), std::size_t(page_size()));
+		ret = ::_aligned_malloc(std::size_t(bytes), std::size_t(page_size()));
 #elif defined TORRENT_BEOS
 		area_id id = create_area("", &ret, B_ANY_ADDRESS
 			, (bytes + page_size() - 1) & (page_size() - 1), B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
diff --git a/src/assert.cpp b/src/assert.cpp
index b0c5b9c9c..3c4d355ec 100644
--- a/src/assert.cpp
+++ b/src/assert.cpp
@@ -68,7 +68,7 @@ std::string demangle(char const* name)
 {
 // in case this string comes
 	// this is needed on linux
-	char const* start = strchr(name, '(');
+	char const* start = std::strchr(name, '(');
 	if (start != nullptr)
 	{
 		++start;
@@ -79,14 +79,14 @@ std::string demangle(char const* name)
 		start = strstr(name, "0x");
 		if (start != nullptr)
 		{
-			start = strchr(start, ' ');
+			start = std::strchr(start, ' ');
 			if (start != nullptr) ++start;
 			else start = name;
 		}
 		else start = name;
 	}
 
-	char const* end = strchr(start, '+');
+	char const* end = std::strchr(start, '+');
 	if (end) while (*(end-1) == ' ') --end;
 
 	std::string in;
@@ -98,7 +98,7 @@ std::string demangle(char const* name)
 	char* unmangled = ::abi::__cxa_demangle(in.c_str(), nullptr, &len, &status);
 	if (unmangled == nullptr) return in;
 	std::string ret(unmangled);
-	free(unmangled);
+	::free(unmangled);
 	return ret;
 }
 #elif defined _WIN32
@@ -129,8 +129,8 @@ std::string demangle(char const* name) { return name; }
 TORRENT_EXPORT void print_backtrace(char* out, int len, int max_depth, void*)
 {
 	void* stack[50];
-	int size = backtrace(stack, 50);
-	char** symbols = backtrace_symbols(stack, size);
+	int size = ::backtrace(stack, 50);
+	char** symbols = ::backtrace_symbols(stack, size);
 
 	for (int i = 1; i < size && len > 0; ++i)
 	{
@@ -140,7 +140,7 @@ TORRENT_EXPORT void print_backtrace(char* out, int len, int max_depth, void*)
 		if (i - 1 == max_depth && max_depth > 0) break;
 	}
 
-	free(symbols);
+	::free(symbols);
 }
 
 #elif defined _WIN32
@@ -292,7 +292,7 @@ TORRENT_EXPORT void assert_print(char const* fmt, ...)
 #endif
 	va_list va;
 	va_start(va, fmt);
-	vfprintf(out, fmt, va);
+	std::vfprintf(out, fmt, va);
 	va_end(va);
 
 #ifdef TORRENT_PRODUCTION_ASSERTS
@@ -358,9 +358,9 @@ TORRENT_EXPORT void assert_fail(char const* expr, int line
 #else
 	// send SIGINT to the current process
 	// to break into the debugger
-	raise(SIGINT);
+	::raise(SIGINT);
 #endif
-	abort();
+	::abort();
 #endif
 }
 
diff --git a/src/bdecode.cpp b/src/bdecode.cpp
index 446306bc6..bcd2fbd35 100644
--- a/src/bdecode.cpp
+++ b/src/bdecode.cpp
@@ -227,6 +227,7 @@ namespace {
 
 	bdecode_node& bdecode_node::operator=(bdecode_node const& n)
 	{
+		if (&n == this) return *this;
 		m_tokens = n.m_tokens;
 		m_root_tokens = n.m_root_tokens;
 		m_buffer = n.m_buffer;
@@ -660,10 +661,9 @@ namespace {
 		// +1 is to skip the 'i'
 		char const* ptr = m_buffer + t.offset + 1;
 		std::int64_t val = 0;
-		bool negative = false;
-		if (*ptr == '-') negative = true;
+		bool const negative = (*ptr == '-');
 		bdecode_errors::error_code_enum ec = bdecode_errors::no_error;
-		char const* end = parse_int(ptr + negative
+		char const* end = parse_int(ptr + int(negative)
 			, ptr + size, 'e', val, ec);
 		if (ec) return 0;
 		TORRENT_UNUSED(end);
diff --git a/src/bitfield.cpp b/src/bitfield.cpp
index d2b9cae68..80ef8e38c 100644
--- a/src/bitfield.cpp
+++ b/src/bitfield.cpp
@@ -141,7 +141,7 @@ namespace libtorrent {
 		int const new_size_words = num_words();
 		if (val)
 		{
-			if (old_size_words && b) buf()[old_size_words - 1] |= aux::host_to_network((0xffffffff >> b));
+			if (old_size_words && b) buf()[old_size_words - 1] |= aux::host_to_network(0xffffffff >> b);
 			if (old_size_words < new_size_words)
 				std::memset(buf() + old_size_words, 0xff
 					, std::size_t((new_size_words - old_size_words) * 4));
diff --git a/src/block_cache.cpp b/src/block_cache.cpp
index 492ebf5c0..92c9b40da 100644
--- a/src/block_cache.cpp
+++ b/src/block_cache.cpp
@@ -1328,7 +1328,7 @@ bool block_cache::inc_block_refcount(cached_piece_entry* pe, int block, int reas
 		case ref_hashing: ++pe->blocks[block].hashing_count; break;
 		case ref_reading: ++pe->blocks[block].reading_count; break;
 		case ref_flushing: ++pe->blocks[block].flushing_count; break;
-	};
+	}
 	TORRENT_ASSERT(int(pe->blocks[block].refcount) >= pe->blocks[block].hashing_count
 		+ pe->blocks[block].reading_count + pe->blocks[block].flushing_count);
 #else
@@ -1361,7 +1361,7 @@ void block_cache::dec_block_refcount(cached_piece_entry* pe, int block, int reas
 		case ref_hashing: --pe->blocks[block].hashing_count; break;
 		case ref_reading: --pe->blocks[block].reading_count; break;
 		case ref_flushing: --pe->blocks[block].flushing_count; break;
-	};
+	}
 	TORRENT_PIECE_ASSERT(int(pe->blocks[block].refcount) >= pe->blocks[block].hashing_count
 		+ pe->blocks[block].reading_count + pe->blocks[block].flushing_count, pe);
 #else
diff --git a/src/bt_peer_connection.cpp b/src/bt_peer_connection.cpp
index cdeedcd90..8a07ff816 100644
--- a/src/bt_peer_connection.cpp
+++ b/src/bt_peer_connection.cpp
@@ -2400,11 +2400,11 @@ namespace {
 		if (!m_enc_handler.is_recv_plaintext())
 		{
 			int const consumed = m_enc_handler.decrypt(m_recv_buffer, bytes_transferred);
-	#ifndef TORRENT_DISABLE_LOGGING
+#ifndef TORRENT_DISABLE_LOGGING
 			if (consumed + int(bytes_transferred) > 0)
 				peer_log(peer_log_alert::incoming_message, "ENCRYPTION"
 					, "decrypted block s = %d", consumed + int(bytes_transferred));
-	#endif
+#endif
 			if (bytes_transferred == SIZE_MAX)
 			{
 				disconnect(errors::parse_failed, operation_t::encryption);
@@ -2424,21 +2424,21 @@ namespace {
 			while (bytes_transferred > 0 &&
 				((sub_transferred = m_recv_buffer.advance_pos(int(bytes_transferred))) > 0))
 			{
-	#if TORRENT_USE_ASSERTS
-				std::int64_t cur_payload_dl = m_statistics.last_payload_downloaded();
-				std::int64_t cur_protocol_dl = m_statistics.last_protocol_downloaded();
-	#endif
+#if TORRENT_USE_ASSERTS
+				std::int64_t const cur_payload_dl = m_statistics.last_payload_downloaded();
+				std::int64_t const cur_protocol_dl = m_statistics.last_protocol_downloaded();
+#endif
 				TORRENT_ASSERT(sub_transferred > 0);
 				on_receive_impl(std::size_t(sub_transferred));
 				bytes_transferred -= std::size_t(sub_transferred);
 
-	#if TORRENT_USE_ASSERTS
+#if TORRENT_USE_ASSERTS
 				TORRENT_ASSERT(m_statistics.last_payload_downloaded() - cur_payload_dl >= 0);
 				TORRENT_ASSERT(m_statistics.last_protocol_downloaded() - cur_protocol_dl >= 0);
-				std::int64_t stats_diff = m_statistics.last_payload_downloaded() - cur_payload_dl +
+				std::int64_t const stats_diff = m_statistics.last_payload_downloaded() - cur_payload_dl +
 					m_statistics.last_protocol_downloaded() - cur_protocol_dl;
 				TORRENT_ASSERT(stats_diff == int(sub_transferred));
-	#endif
+#endif
 
 				if (m_disconnecting) return;
 			}
@@ -3098,7 +3098,7 @@ namespace {
 
 #ifndef TORRENT_DISABLE_EXTENSIONS
 			std::memcpy(m_reserved_bits.data(), recv_buffer.begin(), 8);
-			if ((recv_buffer[5] & 0x10))
+			if (recv_buffer[5] & 0x10)
 				m_supports_extensions = true;
 #endif
 			if (recv_buffer[7] & 0x01)
diff --git a/src/choker.cpp b/src/choker.cpp
index cd395397c..59bae07b2 100644
--- a/src/choker.cpp
+++ b/src/choker.cpp
@@ -55,25 +55,22 @@ namespace libtorrent {
 		std::shared_ptr<torrent> t2 = rhs->associated_torrent().lock();
 		TORRENT_ASSERT(t2);
 
-		int prio1 = lhs->get_priority(peer_connection::upload_channel);
-		int prio2 = rhs->get_priority(peer_connection::upload_channel);
+		int const prio1 = lhs->get_priority(peer_connection::upload_channel);
+		int const prio2 = rhs->get_priority(peer_connection::upload_channel);
 
-		if (prio1 != prio2)
-			return prio1 > prio2;
+		if (prio1 != prio2) return prio1 > prio2;
 
 		// compare how many bytes they've sent us
-		std::int64_t c1;
-		std::int64_t c2;
-		c1 = lhs->downloaded_in_last_round();
-		c2 = rhs->downloaded_in_last_round();
+		std::int64_t const d1 = lhs->downloaded_in_last_round();
+		std::int64_t const d2 = rhs->downloaded_in_last_round();
 
-		if (c1 != c2) return c1 > c2;
+		if (d1 != d2) return d1 > d2;
 
 		// when seeding, rotate which peer is unchoked in a round-robin fasion
 
 		// the amount uploaded since unchoked (not just in the last round)
-		c1 = lhs->uploaded_since_unchoked();
-		c2 = rhs->uploaded_since_unchoked();
+		std::int64_t const u1 = lhs->uploaded_since_unchoked();
+		std::int64_t const u2 = rhs->uploaded_since_unchoked();
 
 		// the way the round-robin unchoker works is that it,
 		// by default, prioritizes any peer that is already unchoked.
@@ -84,17 +81,17 @@ namespace libtorrent {
 		// if a peer is already unchoked, the number of bytes sent since it was unchoked
 		// is greater than the send quanta, and it has been unchoked for at least one minute
 		// then it's done with its upload slot, and we can de-prioritize it
-		bool c1_quota_complete = !lhs->is_choked()
-			&& c1 > t1->torrent_file().piece_length() * pieces
+		bool const c1_quota_complete = !lhs->is_choked()
+			&& u1 > t1->torrent_file().piece_length() * pieces
 			&& aux::time_now() - lhs->time_of_last_unchoke() > minutes(1);
-		bool c2_quota_complete = !rhs->is_choked()
-			&& c2 > t2->torrent_file().piece_length() * pieces
+		bool const c2_quota_complete = !rhs->is_choked()
+			&& u2 > t2->torrent_file().piece_length() * pieces
 			&& aux::time_now() - rhs->time_of_last_unchoke() > minutes(1);
 
 		// if c2 has completed a quanta, it should be de-prioritized
 		// and vice versa
-		if (c1_quota_complete < c2_quota_complete) return true;
-		if (c1_quota_complete > c2_quota_complete) return false;
+		if (c1_quota_complete != c2_quota_complete)
+			return int(c1_quota_complete) < int(c2_quota_complete);
 
 		// when seeding, prefer the peer we're uploading the fastest to
 
@@ -103,11 +100,10 @@ namespace libtorrent {
 		// there may have been a residual transfer which was already
 		// in-flight at the time and we don't want that to cause the peer
 		// to be ranked at the top of the choked peers
-		c1 = lhs->is_choked() ? 0 : lhs->uploaded_in_last_round();
-		c2 = rhs->is_choked() ? 0 : rhs->uploaded_in_last_round();
+		std::int64_t const c1 = lhs->is_choked() ? 0 : lhs->uploaded_in_last_round();
+		std::int64_t const c2 = rhs->is_choked() ? 0 : rhs->uploaded_in_last_round();
 
-		if (c1 > c2) return true;
-		if (c2 > c1) return false;
+		if (c1 != c2) return c1 > c2;
 
 		// if the peers are still identical (say, they're both waiting to be unchoked)
 		// prioritize the one that has waited the longest to be unchoked
diff --git a/src/create_torrent.cpp b/src/create_torrent.cpp
index 8c6d6983b..cad33580f 100644
--- a/src/create_torrent.cpp
+++ b/src/create_torrent.cpp
@@ -312,7 +312,7 @@ namespace {
 	create_torrent::create_torrent(file_storage& fs, int piece_size
 		, int pad_file_limit, create_flags_t const flags, int alignment)
 		: m_files(fs)
-		, m_creation_date(time(nullptr))
+		, m_creation_date(::time(nullptr))
 		, m_multifile(fs.num_files() > 1)
 		, m_private(false)
 		, m_merkle_torrent(bool(flags & create_torrent::merkle))
@@ -372,7 +372,7 @@ namespace {
 
 	create_torrent::create_torrent(torrent_info const& ti)
 		: m_files(const_cast<file_storage&>(ti.files()))
-		, m_creation_date(time(0))
+		, m_creation_date(::time(0))
 		, m_multifile(ti.num_files() > 1)
 		, m_private(ti.priv())
 		, m_merkle_torrent(ti.is_merkle_torrent())
diff --git a/src/disk_buffer_holder.cpp b/src/disk_buffer_holder.cpp
index abeee7b13..e4291ca3f 100644
--- a/src/disk_buffer_holder.cpp
+++ b/src/disk_buffer_holder.cpp
@@ -42,6 +42,7 @@ namespace libtorrent {
 
 	disk_buffer_holder& disk_buffer_holder::operator=(disk_buffer_holder&& h) noexcept
 	{
+		if (&h == this) return *this;
 		disk_buffer_holder(std::move(h)).swap(*this);
 		return *this;
 	}
diff --git a/src/disk_io_thread.cpp b/src/disk_io_thread.cpp
index ffea93fd7..45b986ac2 100644
--- a/src/disk_io_thread.cpp
+++ b/src/disk_io_thread.cpp
@@ -170,6 +170,7 @@ namespace libtorrent {
 		{ rhs.m_lock = nullptr; }
 		scoped_unlocker_impl& operator=(scoped_unlocker_impl&& rhs)
 		{
+			if (&rhs == this) return *this;
 			if (m_lock) m_lock->lock();
 			m_lock = rhs.m_lock;
 			rhs.m_lock = nullptr;
@@ -445,6 +446,7 @@ constexpr disk_job_flags_t disk_interface::cache_hit;
 				continue;
 			}
 
+#if DEBUG_DISK_THREAD
 			if (pe->num_dirty < pe->blocks_in_piece)
 			{
 				DLOG("[%d dirty:%d] ", static_cast<int>(i), int(pe->num_dirty));
@@ -457,6 +459,7 @@ constexpr disk_job_flags_t disk_interface::cache_hit;
 			{
 				DLOG("[%d xx] ", static_cast<int>(i));
 			}
+#endif
 
 			// TODO: in this case, the piece should probably not be flushed yet. are there
 			// any more cases where it should?
diff --git a/src/entry.cpp b/src/entry.cpp
index 91b6dc6a0..aa30caa5b 100644
--- a/src/entry.cpp
+++ b/src/entry.cpp
@@ -61,7 +61,7 @@ namespace detail {
 		}
 		buf[--size] = '\0';
 		if (val == 0) buf[--size] = '0';
-		for (; size > sign && val != 0;)
+		while (size > sign && val != 0)
 		{
 			buf[--size] = '0' + char(val % 10);
 			val /= 10;
@@ -147,6 +147,7 @@ namespace {
 
 	entry& entry::operator=(entry&& e) noexcept
 	{
+		if (&e == this) return *this;
 		swap(e);
 		return *this;
 	}
diff --git a/src/enum_net.cpp b/src/enum_net.cpp
index 5f6106776..2e3b8c67a 100644
--- a/src/enum_net.cpp
+++ b/src/enum_net.cpp
@@ -74,7 +74,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <netinet/ether.h>
 #include <netinet/in.h>
 #include <net/if.h>
-#include <stdio.h>
+#include <cstdio>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
@@ -216,7 +216,7 @@ namespace {
 		// first byte of routing messages is always the family
 		msg[sizeof(nlmsghdr)] = family;
 
-		if (send(sock, nl_msg, nl_msg->nlmsg_len, 0) < 0)
+		if (::send(sock, nl_msg, nl_msg->nlmsg_len, 0) < 0)
 		{
 			return -1;
 		}
@@ -224,7 +224,7 @@ namespace {
 		// get the socket's port ID so that we can verify it in the repsonse
 		sockaddr_nl sock_addr;
 		socklen_t sock_addr_len = sizeof(sock_addr);
-		if (getsockname(sock, reinterpret_cast<sockaddr*>(&sock_addr), &sock_addr_len) < 0)
+		if (::getsockname(sock, reinterpret_cast<sockaddr*>(&sock_addr), &sock_addr_len) < 0)
 		{
 			return -1;
 		}
@@ -285,10 +285,10 @@ namespace {
 #endif
 
 		ifreq req = {};
-		if_indextoname(std::uint32_t(if_index), req.ifr_name);
+		::if_indextoname(std::uint32_t(if_index), req.ifr_name);
 		static_assert(sizeof(rt_info->name) >= sizeof(req.ifr_name), "ip_route::name is too small");
 		std::memcpy(rt_info->name, req.ifr_name, sizeof(req.ifr_name));
-		ioctl(s, siocgifmtu, &req);
+		::ioctl(s, ::siocgifmtu, &req);
 		rt_info->mtu = req.ifr_mtu;
 //		obviously this doesn't work correctly. How do you get the netmask for a route?
 //		if (ioctl(s, SIOCGIFNETMASK, &req) == 0) {
@@ -549,7 +549,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 			ret.push_back(wan);
 		}
 #elif TORRENT_USE_NETLINK
-		int sock = socket(PF_ROUTE, SOCK_DGRAM, NETLINK_ROUTE);
+		int sock = ::socket(PF_ROUTE, SOCK_DGRAM, NETLINK_ROUTE);
 		if (sock < 0)
 		{
 			ec = error_code(errno, system_category());
@@ -562,7 +562,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		if (len < 0)
 		{
 			ec = error_code(errno, system_category());
-			close(sock);
+			::close(sock);
 			return ret;
 		}
 
@@ -581,9 +581,9 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 #pragma clang diagnostic pop
 #endif
 
-		close(sock);
+		::close(sock);
 #elif TORRENT_USE_IFADDRS
-		int s = socket(AF_INET, SOCK_DGRAM, 0);
+		int s = ::socket(AF_INET, SOCK_DGRAM, 0);
 		if (s < 0)
 		{
 			ec = error_code(errno, system_category());
@@ -594,7 +594,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		if (getifaddrs(&ifaddr) == -1)
 		{
 			ec = error_code(errno, system_category());
-			close(s);
+			::close(s);
 			return ret;
 		}
 
@@ -610,11 +610,11 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 					ret.push_back(iface);
 			}
 		}
-		close(s);
+		::close(s);
 		freeifaddrs(ifaddr);
 // MacOS X, BSD and solaris
 #elif TORRENT_USE_IFCONF
-		int s = socket(AF_INET, SOCK_DGRAM, 0);
+		int s = ::socket(AF_INET, SOCK_DGRAM, 0);
 		if (s < 0)
 		{
 			ec = error_code(errno, system_category());
@@ -628,7 +628,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		if (ioctl(s, SIOCGIFCONF, &ifc) < 0)
 		{
 			ec = error_code(errno, system_category());
-			close(s);
+			::close(s);
 			return ret;
 		}
 
@@ -669,7 +669,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 #endif
 					{
 						ec = error_code(errno, system_category());
-						close(s);
+						::close(s);
 						return ret;
 					}
 				}
@@ -683,7 +683,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 			ifr += current_size;
 			remaining -= current_size;
 		}
-		close(s);
+		::close(s);
 
 #elif TORRENT_USE_GETADAPTERSADDRESSES
 
@@ -736,7 +736,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		}
 #endif
 
-		SOCKET s = socket(AF_INET, SOCK_DGRAM, 0);
+		SOCKET s = ::socket(AF_INET, SOCK_DGRAM, 0);
 		if (int(s) == SOCKET_ERROR)
 		{
 			ec = error_code(WSAGetLastError(), system_category());
@@ -855,7 +855,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		m.m_rtm.rtm_seq = 0;
 		m.m_rtm.rtm_msglen = len;
 
-		int s = socket(PF_ROUTE, SOCK_RAW, AF_UNSPEC);
+		int s = ::socket(PF_ROUTE, SOCK_RAW, AF_UNSPEC);
 		if (s == -1)
 		{
 			ec = error_code(errno, system_category());
@@ -866,13 +866,13 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		if (n == -1)
 		{
 			ec = error_code(errno, system_category());
-			close(s);
+			::close(s);
 			return std::vector<ip_route>();
 		}
 		else if (n != len)
 		{
 			ec = boost::asio::error::operation_not_supported;
-			close(s);
+			::close(s);
 			return std::vector<ip_route>();
 		}
 		bzero(&m, len);
@@ -881,7 +881,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		if (n == -1)
 		{
 			ec = error_code(errno, system_category());
-			close(s);
+			::close(s);
 			return std::vector<ip_route>();
 		}
 
@@ -936,7 +936,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 			r.netmask = sockaddr_to_address((sockaddr*)p);
 			ret.push_back(r);
 		}
-		close(s);
+		::close(s);
 */
 	int mib[6] = {CTL_NET, PF_ROUTE, 0, AF_UNSPEC, NET_RT_DUMP, 0};
 
@@ -975,7 +975,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 
 	char* end = buf.get() + needed;
 
-	int s = socket(AF_INET, SOCK_DGRAM, 0);
+	int s = ::socket(AF_INET, SOCK_DGRAM, 0);
 	if (s < 0)
 	{
 		ec = error_code(errno, system_category());
@@ -995,7 +995,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		ip_route r;
 		if (parse_route(s, rtm, &r)) ret.push_back(r);
 	}
-	close(s);
+	::close(s);
 
 #elif TORRENT_USE_GETIPFORWARDTABLE
 /*
@@ -1142,7 +1142,7 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		// Free memory
 		free(routes);
 #elif TORRENT_USE_NETLINK
-		int sock = socket(PF_ROUTE, SOCK_DGRAM, NETLINK_ROUTE);
+		int sock = ::socket(PF_ROUTE, SOCK_DGRAM, NETLINK_ROUTE);
 		if (sock < 0)
 		{
 			ec = error_code(errno, system_category());
@@ -1157,11 +1157,11 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 		if (len < 0)
 		{
 			ec = error_code(errno, system_category());
-			close(sock);
+			::close(sock);
 			return std::vector<ip_route>();
 		}
 
-		int s = socket(AF_INET, SOCK_DGRAM, 0);
+		int s = ::socket(AF_INET, SOCK_DGRAM, 0);
 		if (s < 0)
 		{
 			ec = error_code(errno, system_category());
@@ -1181,8 +1181,8 @@ int _System __libsocket_sysctl(int* mib, u_int namelen, void *oldp, size_t *oldl
 #ifdef __clang__
 #pragma clang diagnostic pop
 #endif
-		close(s);
-		close(sock);
+		::close(s);
+		::close(sock);
 
 #endif
 		return ret;
diff --git a/src/escape_string.cpp b/src/escape_string.cpp
index 663f6f1d2..8e1ce1dcf 100644
--- a/src/escape_string.cpp
+++ b/src/escape_string.cpp
@@ -560,7 +560,7 @@ namespace {
 		// posix has a weird iconv signature. implementations
 		// differ on what this signature should be, so we use
 		// a macro to let config.hpp determine it
-		size_t retval = iconv(h, TORRENT_ICONV_ARG(&in), &insize,
+		size_t retval = ::iconv(h, TORRENT_ICONV_ARG(&in), &insize,
 			&out, &outsize);
 		if (retval == size_t(-1)) return s;
 		// if this string has an invalid utf-8 sequence in it, don't touch it
@@ -581,7 +581,7 @@ namespace {
 		std::lock_guard<std::mutex> l(iconv_mutex);
 
 		// the empty string represents the local dependent encoding
-		static iconv_t iconv_handle = iconv_open("", "UTF-8");
+		static iconv_t iconv_handle = ::iconv_open("", "UTF-8");
 		if (iconv_handle == iconv_t(-1)) return s;
 		return iconv_convert_impl(s, iconv_handle);
 	}
@@ -593,7 +593,7 @@ namespace {
 		std::lock_guard<std::mutex> l(iconv_mutex);
 
 		// the empty string represents the local dependent encoding
-		static iconv_t iconv_handle = iconv_open("UTF-8", "");
+		static iconv_t iconv_handle = ::iconv_open("UTF-8", "");
 		if (iconv_handle == iconv_t(-1)) return s;
 		return iconv_convert_impl(s, iconv_handle);
 	}
diff --git a/src/file.cpp b/src/file.cpp
index b40adb3a3..333749d30 100644
--- a/src/file.cpp
+++ b/src/file.cpp
@@ -381,7 +381,7 @@ static_assert(!(open_mode::sparse & open_mode::attribute_mask), "internal flags
 		if (m_handle != INVALID_HANDLE_VALUE)
 			FindClose(m_handle);
 #else
-		if (m_handle) closedir(m_handle);
+		if (m_handle) ::closedir(m_handle);
 #endif
 	}
 
@@ -638,11 +638,11 @@ static_assert(!(open_mode::sparse & open_mode::attribute_mask), "internal flags
 		if ((mode & open_mode::no_cache))
 		{
 			int yes = 1;
-			fcntl(native_handle(), F_NOCACHE, &yes);
+			::fcntl(native_handle(), F_NOCACHE, &yes);
 
 #ifdef F_NODIRECT
 			// it's OK to temporarily cache written pages
-			fcntl(native_handle(), F_NODIRECT, &yes);
+			::fcntl(native_handle(), F_NODIRECT, &yes);
 #endif
 		}
 #endif
@@ -651,7 +651,7 @@ static_assert(!(open_mode::sparse & open_mode::attribute_mask), "internal flags
 		if ((mode & open_mode::random_access))
 		{
 			// disable read-ahead
-			posix_fadvise(native_handle(), 0, 0, POSIX_FADV_RANDOM);
+			::posix_fadvise(native_handle(), 0, 0, POSIX_FADV_RANDOM);
 		}
 #endif
 
@@ -1048,7 +1048,7 @@ namespace {
 	!defined DIRECTIO_ON
 		if (m_open_mode & open_mode::no_cache)
 		{
-			if (fdatasync(native_handle()) != 0
+			if (::fdatasync(native_handle()) != 0
 				&& errno != EINVAL
 				&& errno != ENOSYS)
 			{
@@ -1197,7 +1197,7 @@ namespace {
 #endif // if Windows Vista
 #else // NON-WINDOWS
 		struct stat st;
-		if (fstat(native_handle(), &st) != 0)
+		if (::fstat(native_handle(), &st) != 0)
 		{
 			ec.assign(errno, system_category());
 			return false;
@@ -1205,7 +1205,7 @@ namespace {
 
 		// only truncate the file if it doesn't already
 		// have the right size. We don't want to update
-		if (st.st_size != s && ftruncate(native_handle(), s) < 0)
+		if (st.st_size != s && ::ftruncate(native_handle(), s) < 0)
 		{
 			ec.assign(errno, system_category());
 			return false;
@@ -1286,7 +1286,7 @@ namespace {
 		return file_size.QuadPart;
 #else
 		struct stat fs;
-		if (fstat(native_handle(), &fs) != 0)
+		if (::fstat(native_handle(), &fs) != 0)
 		{
 			ec.assign(errno, system_category());
 			return -1;
@@ -1338,7 +1338,7 @@ typedef struct _FILE_ALLOCATED_RANGE_BUFFER {
 
 #elif defined SEEK_DATA
 		// this is supported on solaris
-		std::int64_t ret = lseek(native_handle(), start, SEEK_DATA);
+		std::int64_t ret = ::lseek(native_handle(), start, SEEK_DATA);
 		if (ret < 0) return start;
 		return start;
 #else
diff --git a/src/file_storage.cpp b/src/file_storage.cpp
index cd6a0f3ea..99827b3ca 100644
--- a/src/file_storage.cpp
+++ b/src/file_storage.cpp
@@ -216,7 +216,7 @@ namespace {
 
 	internal_file_entry::~internal_file_entry()
 	{
-		if (name_len == name_is_owned) free(const_cast<char*>(name));
+		if (name_len == name_is_owned) ::free(const_cast<char*>(name));
 	}
 
 	internal_file_entry::internal_file_entry(internal_file_entry const& fe)
@@ -240,6 +240,7 @@ namespace {
 
 	internal_file_entry& internal_file_entry::operator=(internal_file_entry const& fe)
 	{
+		if (&fe == this) return *this;
 		offset = fe.offset;
 		size = fe.size;
 		path_index = fe.path_index;
@@ -272,6 +273,7 @@ namespace {
 
 	internal_file_entry& internal_file_entry::operator=(internal_file_entry&& fe) noexcept
 	{
+		if (&fe == this) return *this;
 		offset = fe.offset;
 		size = fe.size;
 		path_index = fe.path_index;
@@ -303,7 +305,7 @@ namespace {
 		if (string_len >= name_is_owned) string_len = name_is_owned - 1;
 
 		// free the current string, before assigning the new one
-		if (name_len == name_is_owned) free(const_cast<char*>(name));
+		if (name_len == name_is_owned) ::free(const_cast<char*>(name));
 		if (n == nullptr)
 		{
 			TORRENT_ASSERT(borrow_string == false);
diff --git a/src/http_connection.cpp b/src/http_connection.cpp
index 43c5918fd..4c319caa8 100644
--- a/src/http_connection.cpp
+++ b/src/http_connection.cpp
@@ -642,7 +642,7 @@ void http_connection::callback(error_code e, span<char> data)
 		data = m_parser.collapse_chunk_headers(data);
 
 		std::string const& encoding = m_parser.header("content-encoding");
-		if ((encoding == "gzip" || encoding == "x-gzip"))
+		if (encoding == "gzip" || encoding == "x-gzip")
 		{
 			error_code ec;
 			inflate_gzip(data, buf, m_max_bottled_buffer_size, ec);
diff --git a/src/i2p_stream.cpp b/src/i2p_stream.cpp
index 45e6fb756..d04b0ac3b 100644
--- a/src/i2p_stream.cpp
+++ b/src/i2p_stream.cpp
@@ -445,8 +445,6 @@ namespace libtorrent {
 				, std::bind(&i2p_stream::read_line, this, _1, h));
 			break;
 		}
-
-		return;
 	}
 
 	void i2p_stream::send_connect(handler_type h)
diff --git a/src/identify_client.cpp b/src/identify_client.cpp
index 3208e842a..55200658e 100644
--- a/src/identify_client.cpp
+++ b/src/identify_client.cpp
@@ -33,6 +33,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <cctype>
 #include <algorithm>
 #include <cstdio>
+#include <cstring>
 
 #include "libtorrent/aux_/disable_warnings_push.hpp"
 #include <boost/optional.hpp>
@@ -45,7 +46,6 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace {
 
-
 	using namespace libtorrent;
 
 	int decode_digit(std::uint8_t c)
@@ -138,7 +138,7 @@ namespace {
 
 	// only support BitTorrentSpecification
 	// must be ordered alphabetically
-	static const map_entry name_map[] =
+	const map_entry name_map[] =
 	{
 		  {"7T", "aTorrent for android"}
 		, {"A",  "ABC"}
@@ -244,7 +244,7 @@ namespace {
 		char const* name;
 	};
 	// non-standard names
-	static const generic_map_entry generic_mappings[] =
+	const generic_map_entry generic_mappings[] =
 	{
 		{0, "Deadman Walking-", "Deadman"}
 		, {5, "Azureus", "Azureus 2.0.3.2"}
@@ -290,9 +290,7 @@ namespace {
 			|| ((lhs.id[0] == rhs.id[0]) && (lhs.id[1] < rhs.id[1]));
 	}
 
-namespace {
-
-	static std::string lookup(fingerprint const& f)
+	std::string lookup(fingerprint const& f)
 	{
 		char identity[200];
 
@@ -320,7 +318,7 @@ namespace {
 		{
 			// if we don't have this client in the list
 			// just use the one or two letter code
-			memcpy(temp, f.name, 2);
+			std::memcpy(temp, f.name, 2);
 			temp[2] = 0;
 			name = temp;
 		}
@@ -336,12 +334,13 @@ namespace {
 
 		return identity;
 	}
-}
+
 	bool find_string(char const* id, char const* search)
 	{
 		return std::equal(search, search + std::strlen(search), id);
 	}
-}
+
+} // anonymous namespace
 
 namespace libtorrent {
 
diff --git a/src/kademlia/dht_storage.cpp b/src/kademlia/dht_storage.cpp
index 2355b6ad3..b3c801e9f 100644
--- a/src/kademlia/dht_storage.cpp
+++ b/src/kademlia/dht_storage.cpp
@@ -183,7 +183,7 @@ namespace {
 		int count() const { return int(samples.size()); }
 	};
 
-	class dht_default_storage final : public dht_storage_interface, boost::noncopyable
+	class dht_default_storage final : public dht_storage_interface
 	{
 	public:
 
@@ -195,6 +195,9 @@ namespace {
 
 		~dht_default_storage() override = default;
 
+		dht_default_storage(dht_default_storage const&) = delete;
+		dht_default_storage& operator=(dht_default_storage const&) = delete;
+
 #ifndef TORRENT_NO_DEPRECATE
 		size_t num_torrents() const override { return m_map.size(); }
 		size_t num_peers() const override
@@ -558,7 +561,7 @@ namespace {
 			m_counters.peers -= std::int32_t(std::distance(new_end, peers.end()));
 			peers.erase(new_end, peers.end());
 			// if we're using less than 1/4 of the capacity free up the excess
-			if (!peers.empty() && peers.capacity() / peers.size() >= 4u)
+			if (!peers.empty() && peers.capacity() / peers.size() >= 4U)
 				peers.shrink_to_fit();
 		}
 
diff --git a/src/kademlia/node.cpp b/src/kademlia/node.cpp
index 4eebc11e0..e4368f2f8 100644
--- a/src/kademlia/node.cpp
+++ b/src/kademlia/node.cpp
@@ -1183,7 +1183,6 @@ void node::incoming_request(msg const& m, entry& e)
 		sha1_hash const target(target_ent.string_ptr());
 		// always return nodes as well as peers
 		write_nodes_entries(target, arg_ent.dict_find_list("want"), reply);
-		return;
 	}
 }
 
diff --git a/src/kademlia/put_data.cpp b/src/kademlia/put_data.cpp
index d9bf4b669..10ae3b63f 100644
--- a/src/kademlia/put_data.cpp
+++ b/src/kademlia/put_data.cpp
@@ -61,9 +61,9 @@ void put_data::set_targets(std::vector<std::pair<node_entry, std::string>> const
 			, p.first.id, p.second);
 		if (!o) return;
 
-	#if TORRENT_USE_ASSERTS
+#if TORRENT_USE_ASSERTS
 		o->m_in_constructor = false;
-	#endif
+#endif
 		m_results.push_back(std::move(o));
 	}
 }
diff --git a/src/lazy_bdecode.cpp b/src/lazy_bdecode.cpp
index 71a6e80d3..ca55df7dc 100644
--- a/src/lazy_bdecode.cpp
+++ b/src/lazy_bdecode.cpp
@@ -36,7 +36,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/lazy_entry.hpp"
 #include "libtorrent/bdecode.hpp" // for error codes
 #include "libtorrent/string_util.hpp" // for is_digit
-#include <cstring>
+#include <cstring> // for memset
 #include <limits> // for numeric_limits
 #include <cstdio> // for snprintf
 #include <cinttypes> // for PRId64 et.al.
@@ -241,10 +241,9 @@ namespace {
 	{
 		TORRENT_ASSERT(m_type == int_t);
 		std::int64_t val = 0;
-		bool negative = false;
-		if (*m_data.start == '-') negative = true;
+		bool const negative = (*m_data.start == '-');
 		bdecode_errors::error_code_enum ec = bdecode_errors::no_error;
-		parse_int(m_data.start + negative
+		parse_int(m_data.start + int(negative)
 			, m_data.start + m_size, 'e', val, ec);
 		if (ec) return 0;
 		if (negative) val = -val;
@@ -605,7 +604,7 @@ namespace {
 	std::string print_entry(lazy_entry const& e, bool single_line, int indent)
 	{
 		char indent_str[200];
-		memset(indent_str, ' ', 200);
+		std::memset(indent_str, ' ', 200);
 		indent_str[0] = ',';
 		indent_str[1] = '\n';
 		indent_str[199] = 0;
diff --git a/src/natpmp.cpp b/src/natpmp.cpp
index e5bd99394..730ba1688 100644
--- a/src/natpmp.cpp
+++ b/src/natpmp.cpp
@@ -45,6 +45,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <cinttypes> // for PRId64 et.al.
 #include <cstdarg>
 #include <functional>
+#include <cstring> // for memcpy
 
 #include "libtorrent/natpmp.hpp"
 #include "libtorrent/io.hpp"
@@ -434,7 +435,7 @@ void natpmp::on_reply(error_code const& e
 	// make a copy of the response packet buffer
 	// to avoid overwriting it in the next receive call
 	char msg_buf[sizeof(m_response_buffer)];
-	memcpy(msg_buf, m_response_buffer, bytes_transferred);
+	std::memcpy(msg_buf, m_response_buffer, bytes_transferred);
 
 	m_socket.async_receive_from(boost::asio::buffer(&m_response_buffer[0]
 		, sizeof(m_response_buffer))
diff --git a/src/peer_connection.cpp b/src/peer_connection.cpp
index d74e476d8..458274dcc 100644
--- a/src/peer_connection.cpp
+++ b/src/peer_connection.cpp
@@ -4065,7 +4065,6 @@ namespace libtorrent {
 #endif
 
 		disconnect(e, operation_t::connect, 1);
-		return;
 	}
 
 	// the error argument defaults to 0, which means deliberate disconnect
diff --git a/src/peer_list.cpp b/src/peer_list.cpp
index a7a6b85af..3fab29700 100644
--- a/src/peer_list.cpp
+++ b/src/peer_list.cpp
@@ -1347,10 +1347,10 @@ namespace libtorrent {
 
 		// prefer to drop peers whose only source is resume data
 		if (lhs_resume_data_source != rhs_resume_data_source)
-			return lhs_resume_data_source > rhs_resume_data_source;
+			return int(lhs_resume_data_source) > int(rhs_resume_data_source);
 
 		if (lhs.connectable != rhs.connectable)
-			return lhs.connectable < rhs.connectable;
+			return int(lhs.connectable) < int(rhs.connectable);
 
 		return lhs.trust_points < rhs.trust_points;
 	}
@@ -1365,9 +1365,9 @@ namespace libtorrent {
 			return lhs->failcount < rhs->failcount;
 
 		// Local peers should always be tried first
-		bool lhs_local = is_local(lhs->address());
-		bool rhs_local = is_local(rhs->address());
-		if (lhs_local != rhs_local) return lhs_local > rhs_local;
+		bool const lhs_local = is_local(lhs->address());
+		bool const rhs_local = is_local(rhs->address());
+		if (lhs_local != rhs_local) return int(lhs_local) > int(rhs_local);
 
 		if (lhs->last_connected != rhs->last_connected)
 			return lhs->last_connected < rhs->last_connected;
@@ -1376,9 +1376,8 @@ namespace libtorrent {
 		int const rhs_rank = source_rank(rhs->peer_source());
 		if (lhs_rank != rhs_rank) return lhs_rank > rhs_rank;
 
-		std::uint32_t lhs_peer_rank = lhs->rank(external, external_port);
-		std::uint32_t rhs_peer_rank = rhs->rank(external, external_port);
-		if (lhs_peer_rank > rhs_peer_rank) return true;
-		return false;
+		std::uint32_t const lhs_peer_rank = lhs->rank(external, external_port);
+		std::uint32_t const rhs_peer_rank = rhs->rank(external, external_port);
+		return lhs_peer_rank > rhs_peer_rank;
 	}
 }
diff --git a/src/performance_counters.cpp b/src/performance_counters.cpp
index 421d32a68..3a71130d5 100644
--- a/src/performance_counters.cpp
+++ b/src/performance_counters.cpp
@@ -61,6 +61,7 @@ namespace libtorrent {
 
 	counters& counters::operator=(counters const& c)
 	{
+		if (&c == this) return *this;
 #ifdef ATOMIC_LLONG_LOCK_FREE
 		for (int i = 0; i < m_stats_counter.end_index(); ++i)
 			m_stats_counter[i].store(
diff --git a/src/torrent.cpp b/src/torrent.cpp
index 5a05050a5..d1189a186 100644
--- a/src/torrent.cpp
+++ b/src/torrent.cpp
@@ -6708,10 +6708,9 @@ namespace libtorrent {
 
 	bool connecting_time_compare(peer_connection const* lhs, peer_connection const* rhs)
 	{
-		bool lhs_connecting = lhs->is_connecting() && !lhs->is_disconnecting();
-		bool rhs_connecting = rhs->is_connecting() && !rhs->is_disconnecting();
-		if (lhs_connecting > rhs_connecting) return false;
-		if (lhs_connecting < rhs_connecting) return true;
+		bool const lhs_connecting = lhs->is_connecting() && !lhs->is_disconnecting();
+		bool const rhs_connecting = rhs->is_connecting() && !rhs->is_disconnecting();
+		if (lhs_connecting != rhs_connecting) return (lhs_connecting < rhs_connecting);
 
 		// a lower value of connected_time means it's been waiting
 		// longer. This is a less-than comparison, so if lhs has
@@ -7770,8 +7769,7 @@ namespace libtorrent {
 			else if (m_state == torrent_status::downloading_metadata
 				|| m_state == torrent_status::downloading
 				|| m_state == torrent_status::finished
-				|| m_state == torrent_status::seeding
-				|| m_state == torrent_status::downloading)
+				|| m_state == torrent_status::seeding)
 			{
 				if (is_finished())
 					is_seeding = true;