Lazy shape analysis

Abstract. Many software model checkers are based on predicate ab-straction. If the verification goal depends on pointer structures, the ap-proach does not work well, because it is difficult to find adequate pred-icate abstractions for the heap. In contrast, shape analysis, which uses graph-based heap abstractions, can provide a compact representation of recursive data structures. We integrate shape analysis into the software model checker Blast. Because shape analysis is expensive, we do not ap-ply it globally. Instead, we ensure that, like predicates, shape graphs are computed and stored locally, only where necessary for proving the verifi-cation goal. To achieve this, we extend lazy abstraction refinement, which so far has been used only for predicate abstractions, to three-valued log-ical structures. This approach does not only increase the precision of model checking, but it also increases the efficiency of shape analysis. We implemented the technique by extending Blast with calls to Tvla.