(Georgia Institute of Technology, 2003)
Orso, Alessandro; Sinha, Saurabh; Harrold, Mary Jean
Understanding data dependences in programs is important for many software-engineering activities, such as program understanding, impact analysis, reverse engineering, and debugging. The presence of pointers, arrays, and structures can cause subtle and complex data dependences that can be difficult to understand. For example, in languages such as C, an assignment made through a pointer dereference can assign a value to one of several variables, none of which may appear syntactically in that statement. In the first part of this paper, we describe two techniques for classifying data dependences in the presence of pointer dereferences. The first technique classifies data dependences based on definition type, use type, and path type. The second technique classifies data dependences based on span. We present empirical results to illustrate the distribution of data-dependence types and spans for a set of real C programs. In the second part of the paper, we discuss two applications of the classification techniques. First, we investigate different ways in which the classification can be used to facilitate data-flow testing and verification. We outline an approach that uses types and spans of data dependences to determine the appropriate verification technique for different data dependences; we present empirical results to illustrate the approach. Second, we present a new slicing paradigm that computes slices based on types of data dependences. Based on the new paradigm, we define an incremental slicing technique that computes a slice in multiple steps. We present empirical results to illustrate the sizes of incremental slices and the potential usefulness of incremental slicing for debugging.
(Georgia Institute of Technology, 2003)
Bowring, James Frederick; Rehg, James M.; Harrold, Mary Jean
A program's behavior is ultimately the collection of all its executions. This collection is diverse, unpredictable, and generally unbounded. Thus it is especially suited to statistical analysis and machine learning techniques. We explore the thesis that 1st- and 2nd-order Markov models of event-transitions are effective predictors of program behavior. We present a technique that models program executions as Markov models, and a clustering method for Markov models that aggregates multiple program executions, yielding a statistical description of program behaviors. With this approach, we can train classifiers to recognize specific behaviors emitted by an execution without knowledge of inputs or outcomes. We evaluate an application of active learning to the efficient refinement of our classifiers by conducting three empirical studies that explore a scenario illustrating automated test plan augmentation. We present a set of potential research questions and applications that our work suggests.