fixed possible data race in mNotifications

libretroshare/src/gxs/rsgenexchange.cc

@@ -163,10 +163,25 @@ void RsGenExchange::tick()
 
 	processRoutingClues() ;
 
-	if(!mNotifications.empty())
 	{
-		notifyChanges(mNotifications);
+		std::vector<RsGxsNotify*> mNotifications_copy;
-		mNotifications.clear();
+
+        // make a non-deep copy of mNotifications so that it can be passed off-mutex to notifyChanged()
+        // that will delete it. The potential high cost of notifyChanges() makes it preferable to call off-mutex.
+		{
+			RS_STACK_MUTEX(mGenMtx);
+			if(!mNotifications.empty())
+			{
+				mNotifications_copy = mNotifications;
+				mNotifications.clear();
+			}
+		}
+
+        // Calling notifyChanges() calls back RsGxsIfaceHelper::receiveChanges() that deletes the pointers in the array
+        // and the array itself.  This is pretty bad and we should normally delete the changes here.
+
+		if(!mNotifications_copy.empty())
+			notifyChanges(mNotifications_copy);
 	}
 
 	// implemented service tick function

libretroshare/src/services/p3gxschannels.cc

@@ -377,6 +377,7 @@ void p3GxsChannels::notifyChanges(std::vector<RsGxsNotify *> &changes)
 	if(!unprocessedGroups.empty())
 		request_SpecificSubscribedGroups(unprocessedGroups);
 
+    // the call below deletes changes and its content.
 	RsGxsIfaceHelper::receiveChanges(changes);
 }