Abstract
One of the major costs of software development is associated with testing and validation of successive versions of software systems. An important problem encountered in testing and validation is memory aliasing, which involves correlation of variables across program versions. This is useful to ensure that existing invariants are preserved in newer versions and to match program execution histories. Recent work in this area has focused on trace-based techniques to better isolate affected regions. A variation of this general approach considers memory operations to generate more refined impact sets. The utility of such an approach eventually relies on the ability to effectively recognize aliases.
In this paper, we address the general memory aliasing problem and present a probabilistic trace-based technique for correlating memory locations across execution traces, and associated variables in program versions. Our approach is based on computing the log-odds ratio, which defines the affinity of locations based on observed patterns. As part of the aliasing process, the traces for initial test inputs are aligned without considering aliasing. From the aligned traces, the log-odds ratio of the memory locations is computed. Subsequently, aliasing is used for alignment of successive traces. Our technique can easily be extended to other applications where detecting aliasing is necessary. As a case study, we implement and use our approach in dynamic impact analysis for detecting variations across program versions. Using detailed experiments on real versions of software systems, we observe significant improvements in detection of affected regions when aliasing occurs.
