{"id":47,"date":"2014-03-25T17:04:07","date_gmt":"2014-03-25T17:04:07","guid":{"rendered":"https:\/\/blogs.scummvm.org\/josejx\/?p=47"},"modified":"2022-05-21T17:07:00","modified_gmt":"2022-05-21T17:07:00","slug":"detour-fixing-the-segfault-part-2","status":"publish","type":"post","link":"https:\/\/blogs.scummvm.org\/josejx\/2014\/03\/25\/detour-fixing-the-segfault-part-2\/","title":{"rendered":"Detour: Fixing the Segfault – Part 2"},"content":{"rendered":"

Continued from the previous entry<\/a><\/i><\/p>\n

With the segfault resolved, the bug no longer crashes ResidualVM, but instead, the game gets stuck, preventing the player from continuing. In the game log, we see some messages that might help us to determine the problem:<\/p>\n

\"\"<\/a>
New Error in the Log, Exposed by Fixing the Segfault<\/figcaption><\/figure>\n

In this error, we see first that the Lua interpreter is printing lua: (null)<\/i>. This indicates that a value was unexpectedly null. The Active Stack<\/i> tells us where this error occurred, much like the backtrace in the previous entry, but for the Lua script. Finally, we see the warning that we added in the previous entry, telling us that there’s a registry key read, SpewOnError<\/i>, which doesn’t cause the segfault anymore because of our fix. So that’s good!<\/p>\n

In the stack trace, we see that this failed on a call to a tag method named (helpfully) function<\/i>, so let’s see if we can find that code. In the EMI Demo, the scripts of interest are located in the MagDemo.lab <\/i>file. Following the same directions as before, unlab<\/i> the file and delua<\/i> the Lua scripts.<\/p>\n

Inside, _options.lua<\/i>, there’s a comment with the original line number, 1503. Search for that and we find that the function called was main_menu.return_to_game<\/i>, which kind of makes sense as to why things are getting fouled up. In the original demo on Windows, pressing F1<\/i> does not bring up the main menu, but rather, does nothing, while pressing ESC <\/i>skips the cutscene.<\/p>\n

It appears that the game is in a wrong state, but it would be helpful to have more information about the problem and more details as to what was run. Let’s enable debugging information in ResidualVM to see if there’s anything else that can help us track this down.<\/p>\n

In ResidualVM, there are debug flags that can be enabled from the command line, like this:<\/p>\n