Yup, start the profiler up, use the application, check the call graph. At 100 MLOC the code base is probably a complete mess. Also, simian is probably your fr

Yup, start the profiler up, use the application, check the call graph. At 100 MLOC the code base is probably a complete mess. Also, simian is probably your friend as it will identify large chunks of duplicate code. As well source control can be your friend, the older the source is the more likely it is to contain useful code. The files with the most changes will usually be where the bugs are.