Event Views and Graph Reductions for Understanding System Level C Code

Concurrent processing, runtime bindings, and an extensive use of aggregate data structures make system level C codes difficult to understand. This paper proposes event views and graph reductions as techniques to facilitate program comprehension. Starting with some domain knowledge, a user can apply these techniques to quickly identify and analyze exactly those parts of the program that are relevant to a given concern. We have built a tool called CVision to demonstrate applicability of the proposed techniques. CVision is an interactive tool that allows the user to: (a) quickly get to the relevant parts of the code; (b) graphically visualize relationships between program elements; and (c) interactively apply different graph reductions to eliminate irrelevant relationships. Using these capabilities, the user can quickly distill a large body of code and extract meaningful views of runtime events that capture the user´s concern. The proposed program comprehension techniques are demonstrated through two case studies based on Linux and XINU operating systems