Technical Program
  Invited Speakers
  Technical Papers
  Practitioner Reports
Educators' Symposium
Doctoral Symposium
Student Research Comp.
Turing Lecture
Social Events
Week at a Glance
Final Program (1.5M .pdf)

Find in Program


view, help

"Finding and Preventing Run-Time Error Handling Mistakes"
Object-Oriented Programming, Systems, Languages and Applications
Home    Program    Housing & Transportation    Registration    Submissions    Wiki    Maps
  > Technical Program > Technical Papers > Verification and Validation

 : Thursday

Finding and Preventing Run-Time Error Handling Mistakes

Meeting Rooms 1-3
Thursday, 11:00, 30 minutes


Westley Weimer, UC Berkeley
George Necula, UC Berkeley

It is difficult to write programs that behave correctly in the presence of run-time errors. Existing programming language features often provide poor support for executing clean-up code and for restoring invariants in such exceptional situations. We present a dataflow analysis for finding a certain class of error-handling mistakes: those that arise from a failure to release resources or to clean up properly along all paths. Many real-world programs violate such resource safety policies because of incorrect error handling. Our flow-sensitive analysis keeps track of outstanding obligations along program paths and does a precise modeling of control flow in the presence of exceptions. Using it, we have found over 800 error handling mistakes almost 4 million lines of Java code. The analysis is unsound and produces false positives, but a few simple filtering rules suffice to remove them in practice. The remaining mistakes were manually verified. These mistakes cause sockets, files and database handles to be leaked along some paths. We present a characterization of the most common causes of those errors and discuss the limitations of exception handling, finalizers and destructors in addressing them. Based on those errors, we propose a programming language feature that keeps track of obligations at run time and ensures that they are discharged. Finally, we present case studies to demonstrate that this feature is natural, efficient, and can improve reliability; for example, retrofitting a 34kLOC program with it resulted in a 0.5% code size decrease, a surprising 17% speed increase (from correctly deallocating resources in the presence of exceptions), and more consistent behavior.