An important property of programming language semantics is that they should be compositional. However, unstructured low-level code contains goto-like commands making it hard to define a semantics that is compositional. In this paper, we follow the ideas of Saabas and Uustalu to structure low-level code. This gives us the possibility to define a compositional denotational semantics based on least fixed points to allow for the use of inductive verification methods. We capture the semantics of communication using finite traces similar to the denotations of CSP. In addition, we examine properties of this semantics and give an example that demonstrates reasoning about communication and jumps. With this semantics, we lay the foundations for a proof calculus that captures both, the semantics of unstructured low-level code and communication.Comment: In Proceedings FESCA 2015, arXiv:1503.0437

No abstract

Formal model refinement aims at preserving safety and liveness properties of models. However, there is usually a verification gap between model and executed code, especially if concurrent processes are involved. The reason for this is that a manual implementation and further code optimizations can introduce implementation errors. In this paper, we present a framework that allows for formally proving a failures refinement between a CSP specification and its low-level implementation. The implementation is given in a generic unstructured language with gotos and an abstract communication instruction. We provide a failures-based denotational semantics of it with an appropriate Hoare calculus. Since failures-based refinement is compositional w.r.t. parallel composition of concurrent components and preserves safety and liveness properties, this contributes to reducing the verification gap between high-level specifications and their low-level implementations.

No abstract