The AutoProof Verifier: Usability by Non-Experts and on Standard Code

Formal verification tools are often developed by experts for experts; as a result, their usability by programmers with little formal methods experience may be severely limited. In this paper, we discuss this general phenomenon with reference to AutoProof: a tool that can verify the full functional correctness of object-oriented software. In particular, we present our experiences of using AutoProof in two contrasting contexts representative of non-expert usage. First, we discuss its usability by students in a graduate course on software verification, who were tasked with verifying implementations of various sorting algorithms. Second, we evaluate its usability in verifying code developed for programming assignments of an undergraduate course. The first scenario represents usability by serious non-experts; the second represents usability on "standard code", developed without full functional verification in mind. We report our experiences and lessons learnt, from which we derive some general suggestions for furthering the development of verification tools with respect to improving their usability.Comment: In Proceedings F-IDE 2015, arXiv:1508.0338

Reasoning About Vote Counting Schemes Using Light-weight and Heavy-weight Methods

We compare and contrast our experiences in specifying, implementing and verifying the monotonicity property of a simple plurality voting scheme using modern light-weight and heavy-weight verification tools

Deductive Verification of Parallel Programs Using Why3

The Message Passing Interface specification (MPI) defines a portable message-passing API used to program parallel computers. MPI programs manifest a number of challenges on what concerns correctness: sent and expected values in communications may not match, resulting in incorrect computations possibly leading to crashes; and programs may deadlock resulting in wasted resources. Existing tools are not completely satisfactory: model-checking does not scale with the number of processes; testing techniques wastes resources and are highly dependent on the quality of the test set. As an alternative, we present a prototype for a type-based approach to programming and verifying MPI like programs against protocols. Protocols are written in a dependent type language designed so as to capture the most common primitives in MPI, incorporating, in addition, a form of primitive recursion and collective choice. Protocols are then translated into Why3, a deductive software verification tool. Source code, in turn, is written in WhyML, the language of the Why3 platform, and checked against the protocol. Programs that pass verification are guaranteed to be communication safe and free from deadlocks. We verified several parallel programs from textbooks using our approach, and report on the outcome.Comment: In Proceedings ICE 2015, arXiv:1508.0459

The Dafny Integrated Development Environment

In recent years, program verifiers and interactive theorem provers have become more powerful and more suitable for verifying large programs or proofs. This has demonstrated the need for improving the user experience of these tools to increase productivity and to make them more accessible to non-experts. This paper presents an integrated development environment for Dafny-a programming language, verifier, and proof assistant-that addresses issues present in most state-of-the-art verifiers: low responsiveness and lack of support for understanding non-obvious verification failures. The paper demonstrates several new features that move the state-of-the-art closer towards a verification environment that can provide verification feedback as the user types and can present more helpful information about the program or failed verifications in a demand-driven and unobtrusive way.Comment: In Proceedings F-IDE 2014, arXiv:1404.578

Lessons from Formally Verified Deployed Software Systems (Extended version)

The technology of formal software verification has made spectacular advances, but how much does it actually benefit the development of practical software? Considerable disagreement remains about the practicality of building systems with mechanically-checked proofs of correctness. Is this prospect confined to a few expensive, life-critical projects, or can the idea be applied to a wide segment of the software industry? To help answer this question, the present survey examines a range of projects, in various application areas, that have produced formally verified systems and deployed them for actual use. It considers the technologies used, the form of verification applied, the results obtained, and the lessons that can be drawn for the software industry at large and its ability to benefit from formal verification techniques and tools. Note: a short version of this paper is also available, covering in detail only a subset of the considered systems. The present version is intended for full reference.Comment: arXiv admin note: text overlap with arXiv:1211.6186 by other author

Towards a formally verified microkernel using the VCC verifier

In this thesis we present the design by contract modular approach to formal verification of an industrial real-time microkernel which was not designed with formal verification in mind. The microkernel module targeted is a particular interrupt manager of xLuna Real Time Operating System (RTOS) for embedded systems built by Critical Software S.A. The annotations were verified automatically using the Microsoft Research Verified C Compiler (VCC) tool to reason about concurrency and safety properties of xLuna kernel. The specifications are based in Hoare-style pre- and post-conditions inlined with the real code. xLuna is a microkernel based on the RTEMS Real-Time Operating System. xLuna extends RTEMS for run a GNU/Linux Operating System, providing a runtime multitasking environment for real-time (RTEMS) and non-real-time (Linux) applications. xLuna runs in a preemptable and concurrent environment. Therefore, we use VCC for reasoning about concurrent executions and some functional and safety properties of xLuna microkernel. VCC is an automated verifier for concurrent C programs that is being developed by Microsoft Research, Redmond, USA and European Microsoft Innovation Center (EMIC), Aachen, Germany. VCC is being built and used for operating system verification which makes it suitable for our verification work. Specifications were added to xLuna code following a modular approach to the verification of a specific microkernel module, namely the Interrupt Request (IRQ) module. The Verified C Compiler (VCC) annotations added cover approximately 80% of the IRQ manager C code (the remaining 20% of the code are relative to auxiliary functions outside the scope of our verification work). All the annotations were automatically verified and proven to be correct