Practical Object-Oriented Back-in-Time Debugging

TL;DR: This paper proposes a practical approach that attempts to keep track of only the relevant data, and keeps object history information together with the regular objects in the application memory so that data not reachable from current application objects is garbage collected.

Abstract: Back-in-time debuggers are extremely useful tools for identifying the causes of bugs. Unfortunately the "omniscient" approaches that try to remember allprevious states are impractical because they consume too much space or they are far too slow. Several approaches rely on heuristics to limit these penalties, but they ultimately end up throwing out too much relevant information. In this paper we propose a practical approach that attempts to keep track of only the relevant data. In contrast to other approaches, we keep object history information together with the regular objects in the application memory. Although seemingly counter-intuitive, this approach has the effect that data not reachable from current application objects (and hence, no longer relevant) is garbage collected. We describe the technical details of our approach, and we present benchmarks that demonstrate that memory consumption stays within practical bounds. Furthermore, the performance penalty is significantly less than with other approaches.