Implementation bugs threaten the soundness of algorithmic software verifiers. Generating correctness certificates for correct programs allows for efficient independent validation of verification results, and thus helps to reveal such bugs. Automatic generation of small, compact correctness proofs for concurrent programs is challenging, as the correctness arguments may depend on the particular interleaving, which can lead to exponential explosion. We present an approach that converts an interleaving-based correctness proof, as generated by many algorithmic verifiers, into a thread-modular correctness proof in the style of Owicki and Gries. We automatically synthesize ghost variables that capture the relevant interleaving information, and abstract away irrelevant details. Our evaluation shows that the approach is efficient in practice and generates compact proofs, compared to a baseline.

Abstract The verification ofUltimate Automizerworks on an SMT-LIB-based model of a C program. If we choose an SMT-LIB theory of (mathematical) integers, the translation is not precise, because we overapproximate bitwise operations. In this paper we present a translation for bitwise operations that improves the precision of this overapproximation.

Abstract Ultimate Taipan integrates trace abstraction with algebraic program analysis on path programs. Taipan supports data race checking in concurrent programs through a reduction to reachability checking. Though the subsequent verification is not tuned for data race checking, the results are encouraging.

Abstract The verification approach of Ultimate Automizer utilizes SMT formulas. This paper presents techniques to keep the size of the formulas small. We focus especially on a normal form, called CommuHash normal form that was easy to implement and had a significant impact on the runtime of our tool.

Abstract Ultimate GemCutter verifies concurrent programs using the CEGAR paradigm, by generalizing from spurious counterexample traces to larger sets of correct traces. We integrate classical CEGAR generalization with orthogonal generalization across interleavings. Thereby, we are able to prove correctness of programs otherwise out-of-reach for interpolation-based verification. The competition results show significant advantages over other concurrency approaches in the Ultimate family.

Abstract Ultimate Taipan is a software model checker that combines trace abstraction with abstract interpretation on path programs. In this year’s version, we replaced our abstract interpretation engine and now use a combination of multiple abstraction functions, fixpoint computation, algebraic program analysis, and SMT solving. Our new approach will allow us to integrate new techniques more easily.