improve error handling during session shutdown

include/libtorrent/aux_/disable_warnings_push.hpp

@@ -52,6 +52,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #endif
 #if __GNUC__ >= 7
 #pragma GCC diagnostic ignored "-Wimplicit-fallthrough"
+#pragma GCC diagnostic ignored "-Wnoexcept-type"
 #endif
 #endif
 

include/libtorrent/aux_/session_impl.hpp

@@ -277,6 +277,13 @@ namespace aux {
 
 			void init_peer_class_filter(bool unlimited_local);
 
+			void call_abort()
+			{
+				auto ptr = shared_from_this();
+				m_io_service.dispatch(make_handler([ptr] { ptr->abort(); }
+					, m_abort_handler_storage, *this));
+			}
+
 #ifndef TORRENT_DISABLE_EXTENSIONS
 			using ext_function_t
 				= std::function<std::shared_ptr<torrent_plugin>(torrent_handle const&, void*)>;
@@ -603,8 +610,8 @@ namespace aux {
 			alert_manager& alerts() override { return m_alerts; }
 			disk_interface& disk_thread() override { return m_disk_thread; }
 
-			void abort();
-			void abort_stage2();
+			void abort() noexcept;
+			void abort_stage2() noexcept;
 
 			torrent_handle find_torrent_handle(sha1_hash const& info_hash);
 
@@ -790,6 +797,8 @@ namespace aux {
 			counters m_stats_counters;
 
 			// this is a pool allocator for torrent_peer objects
+			// torrents and the disk cache (implicitly by holding references to the
+			// torrents) depend on this outliving them.
 			torrent_peer_allocator m_peer_allocator;
 
 			// this vector is used to store the block_info
@@ -1180,6 +1189,13 @@ namespace aux {
 			deadline_timer m_timer;
 			aux::handler_storage<TORRENT_READ_HANDLER_MAX_SIZE> m_tick_handler_storage;
 
+			// abort may not fail and cannot allocate memory
+#ifdef _M_AMD64
+			aux::handler_storage<88> m_abort_handler_storage;
+#else
+			aux::handler_storage<56> m_abort_handler_storage;
+#endif
+
 			// torrents are announced on the local network in a
 			// round-robin fashion. All torrents are cycled through
 			// within the LSD announce interval (which defaults to

src/session.cpp

@@ -403,13 +403,11 @@ namespace {
 	session::~session()
 	{
 		aux::dump_call_profile();
-
 		TORRENT_ASSERT(m_impl);
-		std::shared_ptr<aux::session_impl> ptr = m_impl;
 
 		// capture the shared_ptr in the dispatched function
 		// to keep the session_impl alive
-		m_impl->get_io_service().dispatch([=] { ptr->abort(); });
+		m_impl->call_abort();
 
 		if (m_thread && m_thread.unique())
 		{
@@ -424,7 +422,7 @@ namespace {
 	{
 		// stop calling the alert notify function now, to avoid it thinking the
 		// session is still alive
-		m_impl->alerts().set_notify_function(std::function<void()>());
+		m_impl->alerts().set_notify_function({});
 		return session_proxy(m_io_service, m_thread, m_impl);
 	}
 

src/session_impl.cpp

@@ -174,7 +174,7 @@ using namespace std::placeholders;
 #ifdef BOOST_NO_EXCEPTIONS
 namespace boost {
 
-	void throw_exception(std::exception const& e) { ::abort(); }
+	void throw_exception(std::exception const& e) { std::abort(); }
 }
 #endif
 
@@ -807,7 +807,7 @@ namespace aux {
 		}
 	}
 
-	void session_impl::abort()
+	void session_impl::abort() noexcept
 	{
 		TORRENT_ASSERT(is_single_thread());
 
@@ -818,7 +818,7 @@ namespace aux {
 
 		// at this point we cannot call the notify function anymore, since the
 		// session will become invalid.
-		m_alerts.set_notify_function(std::function<void()>());
+		m_alerts.set_notify_function({});
 
 		// this will cancel requests that are not critical for shutting down
 		// cleanly. i.e. essentially tracker hostname lookups that we're not
@@ -914,11 +914,12 @@ namespace aux {
 		// shutdown_stage2 from there.
 		if (m_undead_peers.empty())
 		{
-			m_io_service.post(std::bind(&session_impl::abort_stage2, this));
+			m_io_service.post(make_handler([this] { abort_stage2(); }
+				, m_abort_handler_storage, *this));
 		}
 	}
 
-	void session_impl::abort_stage2()
+	void session_impl::abort_stage2() noexcept
 	{
 		m_download_rate.close();
 		m_upload_rate.close();
@@ -4123,8 +4124,6 @@ namespace {
 		// if we don't have any connection attempt quota, return
 		if (max_connections <= 0) return;
 
-		INVARIANT_CHECK;
-
 		int steps_since_last_connect = 0;
 		int const num_torrents = int(want_peers_finished.size() + want_peers_download.size());
 		for (;;)

src/torrent.cpp

@@ -8399,7 +8399,7 @@ namespace libtorrent {
 	}
 	catch (...) { handle_exception(); }
 
-	void torrent::on_torrent_aborted() try
+	void torrent::on_torrent_aborted()
 	{
 		TORRENT_ASSERT(is_single_thread());
 
@@ -8407,7 +8407,6 @@ namespace libtorrent {
 		// release the disk io handle
 		m_storage.reset();
 	}
-	catch (...) { handle_exception(); }
 
 	bool torrent::is_paused() const
 	{