On the verification of SCOOP programs

Abstract

In this paper we focus on the development of a toolbox for the verification of programs in the context of SCOOP -an elegant concurrency model, recently formalized based on Rewriting Logic (RL) and Maude. SCOOP is implemented in Eiffel and its applicability is demonstrated also from a practical perspective, in the area of robotics programming. Our contribution consists in devising and integrating an alias analyzer and a Coffman deadlock detector under the roof of the same RL-based semantic framework of SCOOP. This enables using the Maude rewriting engine and its LTL model-checker "for free", in order to perform the analyses of interest. We discuss the limitations of our approach for model-checking deadlocks and provide solutions to the state explosion problem. The latter is mainly caused by the size of the SCOOP formalization which incorporates all the aspects of a real concurrency model. On the aliasing side, we propose an extension of a previously introduced alias calculus based on program expressions, to the setting of unbounded program executions such as infinite loops and recursive calls. Moreover, we devise a corresponding executable specification easily implementable on top of the SCOOP formalization. An important property of our extension is that, in non-concurrent settings, the corresponding alias expressions can be over-approximated in terms of a notion of regular expressions. This further enables us to derive an algorithm that always stops and provides a sound over-approximation of the "may aliasing" information, where soundness stands for the lack of false negatives.

A semantics comparison workbench for a concurrent, asynchronous, distributed programming language

“…Scoop Analysis / Verification. Various analyses for Scoop programs have been proposed, including: using a Scoop virtual machine for checking temporal properties [OTHS09]; checking Coffman's deadlock conditions using an abstract semantics [CM17]; and statically checking code annotated with locking orders for the absence of deadlock [WNM10]. In contrast to our work, these approaches are tied to particular (and now obsolete) execution models, and do not operate on (unannotated) source code.…”