Shape Analysis with Connectors

We extend off-the-shelf shape analyses with the ability to infer numeric relations between directly or indirectly connected heap cells. Specifically, we introduce the concept of connectors, an instrumentation that retains relations between heap cells even if these cells are merged into summary nodes. Managing connectors is based on applying generic fold and expand operations on a numeric abstract domain. Connectors are thus a universal tool to enhance shape analyses with any numeric analysis. We show how connectors provide the ability to infer invariants of non-trivial heap structures such as sorted/skip lists and search trees.