added torrent_error_alert when a torrent encounters an error

docs/manual.rst

@@ -6024,6 +6024,21 @@ generated and the torrent is paused.
 		error_code error;
 	};
 
+torrent_error_alert
+-------------------
+
+This is posted whenever a torrent is transitioned into the error state.
+
+::
+
+	struct torrent_error_alert: torrent_alert
+	{
+		// ...
+		error_code error;
+	};
+
+The ``error`` specifies which error the torrent encountered.
+
 file_renamed_alert
 ------------------
 

include/libtorrent/alert_types.hpp

@@ -1216,6 +1216,22 @@ namespace libtorrent
 		error_code error;
 	};
 
+	struct TORRENT_EXPORT torrent_error_alert: torrent_alert
+	{
+		torrent_error_alert(torrent_handle const& h
+			, error_code const& e)
+			: torrent_alert(h)
+			, error(e)
+		{}
+
+		TORRENT_DEFINE_ALERT(torrent_error_alert);
+
+		const static int static_category = alert::error_notification | alert::status_notification;
+		virtual std::string message() const;
+
+		error_code error;
+	};
+
 
 }
 

src/alert.cpp

@@ -505,5 +505,13 @@ namespace libtorrent {
 		return msg;
 	}
 
+	std::string torrent_error_alert::message() const
+	{
+		char msg[200];
+		snprintf(msg, sizeof(msg), " ERROR: %s", error.message().c_str());
+		return torrent_alert::message() + msg;
+	}
+
+
 } // namespace libtorrent
 

src/torrent.cpp

@@ -5770,6 +5770,9 @@ namespace libtorrent
 		m_error = ec;
 		m_error_file = error_file;
 
+		if (alerts().should_post<torrent_error_alert>())
+			alerts().post_alert(torrent_error_alert(get_handle(), ec));
+
 #if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING || defined TORRENT_LOGGING
 		if (ec)
 		{