RubyPolish: Static Bug Detection in Ruby Programs John Locke Alex Mont

Background FindBugs is a static analysis tool used to identify common bugs in Java programs Ruby is a dynamic, interpreted programming language Idea: Develop a FindBugs-type tool which operates on Ruby programs DRuby provides a means to do this

DRuby DRuby adds static typing to the standard Ruby language To accomplish this, DRuby boils down Ruby code to “Ruby Intermediate Language (RIL)” to allow for simple static analysis RIL provides an easier way to parse Ruby code and identify common programming mistakes

Project Plan Examine FindBugs to determine which detectors are useful for Ruby Implement extensible framework for static analysis using DRuby Implement bug detectors using the framework Test results on existing open-sourceRuby programs

Framework Dataflow Analyses Specified by transfer function Bug Detectors Pattern match based on RIL code structure for common mistakes Takes state and dataflow facts, determines if bug is detected Time permitting: Pluggable interface Conveniently add bug detectors on the fly

Example: Null Pointer Analysis Warning if: -Dereference of NULL or NSP -Nullcheck of NULL or NONNULL NONNULL NSP NCP NULL

Bug Detectors FindBugs has 131 correctness detectors Identified 15 to potentially implement for this project 2 require dataflow analysis 13 require only pattern matching Examples Incompatible bit masks Duplicate conditional tests Useless control flow

Project Progress Compiled and installed DRuby, examined existing code, learned about its operation Implemented prototypes of framework and detectors To do: Continue to fix bugs in the CFG logic Finish implementation of bug detectors Test detectors on existing code

Future Directions Compare with other static analysis tools Extend framework Alias analysis Interprocedural and field analysis Implement additional bug detectors (There’s always something else to detect! ). Possibly implement detectors not present in FindBugs