"Tim Chevalier"
aka a "call graph". This is called "control flow analysis" and the classic paper on it is Olin Shivers' dissertation
This is very well-trodden ground, but if you familiarize yourself with the literature on the subject, then who knows, you may discover something new.
I'll just add that having a tool visualizing this would be very useful for refactoring code. If you e.g. use color to distinguish nodes/functions from different modules, you could use that information to decide to merge or split modules to minimize external interfaces. You could also try to automatically cluster nodes, which would be more interesting theoretically, but IMO less likely to be practical. Another option would be to couple this with profiling or coverage information to visualize something about the usage of paths and nodes in the call graph. -k -- If I haven't seen further, it is by standing in the footprints of giants