While a typical software component has a clearly specified (static) interface in terms of the methods and the input/output types they support, information about the correct sequencing of method calls the client must invoke is usually undocumented. In this paper, we propose a novel solution for automatically extracting such temporal specifications for Java classes. Given a Java class, and a safety property such as "the exception E should not be raised", the corresponding (dynamic) interface is the most general way of invoking the methods in the class so that the safety property is not violated. Our synthesis method first constructs a symbolic representation of the finite state-transition system obtained from the class using predicate abstraction. Constructing the interface then corresponds to solving a partial-information two-player game on this symbolic graph. We present a sound approach to solve this computationally-hard problem approximately using algorithms for learning finite automata and symbolic model checking for branching-time logics. We describe an implementation of the proposed techniques in the tool JIST-Java Interface Synthesis Tool-and demonstrate that the tool can construct interfaces accurately and efficiently for sample Java2SDK library classes.

The natural proof technique for heap verification developed by Qiu et al.[32] provides a platform for powerful sound reasoning for specifications written in a dialect of separation logic called Dryad. Natural proofs are proof tactics that enable automated reasoning exploiting recursion, mimicking common patterns found in human proofs. However, these proofs are known to work only for a simple toy language [32].In this work, we develop a framework called VCDRYAD that extends the VCC framework [9] to provide an automated deductive framework against separation logic specifications for C programs based on natural proofs. We develop several new techniques to build this framework, including (a) a novel tool architecture that allows encoding natural proofs at a higher level in order to use the existing VCC framework (including its intricate memory model, the underlying type-checker, and the SMT-based verification infrastructure), and (b) a synthesis of ghost-code annotations that captures natural proof tactics, in essence forcing VCC to find natural proofs using primarily decidable theories.We evaluate our tool extensively, on more than 150 programs, ranging from code manipulating standard data structures, wellknown open source library routines (Glib, OpenBSD), Linux kernel routines, customized OS data structures, etc. We show that all these C programs can be fully automatically verified using natural proofs (given pre/post conditions and loop invariants) without any user-provided proof tactics. VCDRYAD is perhaps the first deductive verification framework for heap-manipulating programs in a real language that can prove such a wide variety of programs automatically.

We consider the problem of provably verifying that an asynchronous message-passing system satisfies its local assertions. We present a novel reduction scheme for asynchronous event-driven programs that finds almost-synchronous invariants - invariants consisting of global states where message buffers are close to empty. The reduction finds almost-synchronous invariants and simultaneously argues that they cover all local states. We show that asynchronous programs often have almost-synchronous invariants and that we can exploit this to build natural proofs that they are correct. We implement our reduction strategy, which is sound and complete, and show that it is more effective in proving programs correct as well as more efficient in finding bugs in several programs, compared to current search strategies which almost always diverge. The high point of our experiments is that our technique can prove the Windows Phone USB Driver written in P [9]correct for the responsiveness property, which was hitherto not provable using state-of-the-art model-checkers.

We define a new fixpoint modal logic, the visibly pushdown μ-calculus (VP-μ), as an extension of the modal μ-calculus. The models of this logic are execution trees of structured programs where the procedure calls and returns are made visible. This new logic can express pushdown specifications on the model that its classical counterpart cannot, and is motivated by recent work on visibly pushdown languages [4]. We show that our logic naturally captures several interesting program specifications in program verification and dataflow analysis. This includes a variety of program specifications such as computing combinations of local and global program flows, pre/post conditions of procedures, security properties involving the context stack, and interprocedural dataflow analysis properties. The logic can capture flow-sensitive and inter-procedural analysis, and it has constructs that allow skipping procedure calls so that local flows in a procedure can also be tracked. The logic generalizes the semantics of the modal μ-calculus by considering summaries instead of nodes as first-class objects, with appropriate constructs for concatenating summaries, and naturally captures the way in which pushdown models are model-checked. The main result of the paper is that the modelchecking problem for VP-μ is effectively solvable against pushdown models with no more effort than that required for weaker logics such as CTL. We also investigate the expressive power of the logic VP-μ: we show that it encompasses all properties expressed by a corresponding pushdown temporal logic on linear structures (caret [2]) as well as by the classical μ-calculus. This makes VP-μ the most expressive known program logic for which algorithmic software model checking is feasible. In fact, the decidability of most known program logics (μ-calculus, temporal logics LTL and CTL, caret, etc.) can be understood by their interpretation in the monadic second-order logic over trees. This is not true for the logic VP-μ, making it a new powerful tractable program logic. Disciplines Computer SciencesThis conference paper is available AbstractWe define a new fixpoint modal logic, the visibly pushdown µ-calculus (VP-µ), as an extension of the modal µ-calculus. The models of this logic are execution trees of structured programs where the procedure calls and returns are made visible. This new logic can express pushdown specifications on the model that its classical counterpart cannot, and is motivated by recent work on visibly pushdown languages [4]. We show that our logic naturally captures several interesting program specifications in program verification and dataflow analysis. This includes a variety of program specifications such as computing combinations of local and global program flows, pre/post conditions of procedures, security properties involving the context stack, and interprocedural dataflow analysis properties. The logic can capture flow-sensitive and interprocedural analysis, and it has constructs that allow skipping procedure calls so that loca...