CVC4 is the latest version of the Cooperating Validity Checker. A joint project of NYU and U Iowa, CVC4 aims to support the useful feature set of CVC3 and SMT-LIBv2 while optimizing the design of the core system architecture and decision procedures to take advantage of recent engineering and algorithmic advances. CVC4 represents a completely new code base; it is a from-scratch rewrite of CVC3, and many subsystems have been completely redesigned. Additional decision procedures for CVC4 are currently under development, but for what it currently achieves, it is a lighter-weight and higher-performing tool than CVC3. We describe the system architecture, subsystems of note, and discuss some applications and continuing work.

Abstract. Automaton-based static program analysis has proved to be an effective tool for bug finding. Current tools generally re-analyze a program from scratch in response to a change in the code, which can result in much duplicated effort. We present an inter-procedural algorithm that analyzes incrementally in response to program changes and present experiments for a null-pointer dereference analysis. It shows a substantial speed-up over re-analysis from scratch, with a manageable amount of disk space used to store information between analysis runs.

Asynchronous systems components are hard to write, hard to reason about, and (not coincidentally) hard to mechanically verify. In order to achieve high performance, asynchronous code is often written in an event-driven style that introduces non-sequential control flow and persistent heap data to track pending operations. As a result, existing sequential verification and static analysis tools are ineffective on event-driven code.We describe clarity, a programming language that enables analyzable design of asynchronous components. clarity has three novel features: (1) Nonblocking function calls which allow event-driven code to be written in a sequential style. If a blocking statement is encountered during the execution of such a call, the call returns and the remainder of the operation is automatically queued for later execution.(2) Coords, a set of high-level coordination primitives, which encapsulate common interactions between asynchronous components and make high-level coordination protocols explicit. (3) Linearity annotations, which delegate coord protocol obligations to exactly one thread at each asynchronous function call, transforming a concurrent analysis problem into a sequential one.We demonstrate how these language features enable both a more intuitive expression of program logic and more effective program analysis-most checking is done using simple sequential analysis. We describe our experience in developing a network device driver with clarity. We are able to mechanically verify several properties of the clarity driver that are beyond the reach of current analysis technology applied to equivalent C code.

Abstract. It is well known that the use of points-to information can substantially improve the accuracy of a static program analysis. Commonly used algorithms for computing points-to information are known to be sound only for memory-safe programs. Thus, it appears problematic to utilize points-to information to verify the memory safety property without giving up soundness. We show that a sound combination is possible, even if the points-to information is computed separately and only conditionally sound. This result is based on a refined statement of the soundness conditions of points-to analyses and a general mechanism for composing conditionally sound analyses.

No abstract

Device drivers are difficult to write and error-prone. They are usually written in C, a fairly low-level language with minimal type safety and little support for device semantics. As a result, they have become a major source of instability in operating system code.This paper presents NDL, a language for device drivers. NDL provides high-level abstractions of device resources and constructs tailored to describing common device driver operations. We show that NDL allows for the coding of a semantically correct driver with a code size reduction of more than 50% and a minimal impact on performance.

No abstract

No abstract