Abstract. We present an SMT-based symbolic model checking algorithm for safety verification of recursive programs. The algorithm is modular and analyzes procedures individually. Unlike other SMT-based approaches, it maintains both over-and under-approximations of procedure summaries. Under-approximations are used to analyze procedure calls without inlining. Over-approximations are used to block infeasible counterexamples and detect convergence to a proof. We show that for programs and properties over a decidable theory, the algorithm is guaranteed to find a counterexample, if one exists. However, efficiency depends on an oracle for quantifier elimination (QE). For Boolean Programs, the algorithm is a polynomial decision procedure, matching the worst-case bounds of the best BDD-based algorithms. For Linear Arithmetic (integers and rationals), we give an efficient instantiation of the algorithm by applying QE lazily. We use existing interpolation techniques to over-approximate QE and introduce Model Based Projection to underapproximate QE. Empirical evaluation on SV-COMP benchmarks shows that our algorithm improves significantly on the state-of-the-art.

We present a new methodology for automatic verification

We present a new methodology for automatic verification

Implicit invocation or publish-subscribe has become an important architectural style for large-scale system design and evolution. The publish-subscribe style facilitates developing large-scale systems by composing separately developed components because the style permits loose coupling between various components. One of the major bottlenecks in using publish-subscribe systems for very large scale systems is the efficiency of filtering incoming messages, i.e., matching of published events with event subscriptions. This is a very challenging problem because in a realistic publishsubscribe system the number of subscriptions can be large. In this paper we present an approach for matching published events with subscriptions which scales to a large number of subscriptions. Our approach uses Binary Decision Diagrams, a compact data structure for representing boolean functions which has been successfully used in verification techniques such as model checking. Experimental results clearly demonstrate the efficiency of our approach.

Abstract. We present a framework for model checking concurrent software systems which incorporates both states and events. Contrary to other state/event approaches, our work also integrates two powerful verification techniques, counterexample-guided abstraction refinement and compositional reasoning. Our specification language is a state/event extension of linear temporal logic, and allows us to express many properties of software in a concise and intuitive manner. We show how standard automata-theoretic LTL model checking algorithms can be ported to our framework at no extra cost, enabling us to directly benefit from the large body of research on efficient LTL verification. We have implemented this work within our concurrent C model checker, MAGIC, and checked a number of properties of OpenSSL-0.9.6c (an open-source implementation of the SSL protocol) and Micro-C OS version 2 (a real-time operating system for embedded applications). Our experiments show that this new approach not only eases the writing of specifications, but also yields important gains both in space and in time during verification. In certain cases, we even encountered specifications that could not be verified using traditional pure event-based or state-based approaches, but became tractable within our state/event framework. We report a bug in the source code of Micro-C OS version 2, which was found during our experiments.