ORBS: language-independent program slicing

Abstract

Current slicing techniques cannot handle systems written in multiple programming languages. Observation-Based Slicing (ORBS) is a language-independent slicing technique capable of slicing multilanguage systems, including systems which contain (third party) binary components. A potential slice obtained through repeated statement deletion is validated by observing the behaviour of the program: if the slice and original program behave the same under the slicing criterion, the deletion is accepted. The resulting slice is similar to a dynamic slice. We evaluate five variants of ORBS on ten programs of different sizes and languages showing that it is less expensive than similar existing techniques. We also evaluate it on bash and four other systems to demonstrate feasible large-scale operation in which a parallelised ORBS needs up to 82% less time when using four threads. The results show that an ORBS slicer is simple to construct, effective at slicing, and able to handle systems written in multiple languages without specialist analysis tools.

ORBS and the limits of static slicing

“…Observation-Based Slicing is a recently introduced alternative to program slicing [9]: rather than relying on dependency analysis to only perform the allowed deletions, observationbased slicing deletes a statement in a file of interest, executes the program with a given input suite, and observes whether the projected trajectory of the criterion variable changes. If the trajectory changes, the statement cannot be deleted; if it does not change, the statement can be deleted.…”

“…On the other hand, note that the concept of 'statement' can be entirely language independent. Previous work has shown that, by deleting 'lines' in source files rather than program statements, it is possible to slice multi-language systems [9].…”

“…The current implementation of observation-based slicing, ORBS, continuously attempts to delete increasingly longer sequences of lines, starting from each line in the source file [9]. It increases the number of lines to be deleted together, up to the size of the so called 'deletion window'.…”

“…We also have available a recently-produced implementation, ORBS [9], of an observation-based slicing tool. ORBS speculatively deletes lines of code as part of its computation algorithm, attempting to remove one or more statements (lexically), compiling the result (if possible), and then executing using a suite of inputs (taken from test cases).…”

“…Section II presents basic definitions, including the ORBS algorithm [9], section III presents the research questions followed by the results in section IV. Related work is discussed in section V and section VI concludes.…”