Towards Symbolic Execution in Erlang

Abstract

The concurrent functional language Erlang [1] has a number of distinguishing features, like dynamic typing, concurrency via asynchronous message passing or hot code loading, that make it especially appropriate for distributed, faulttolerant, soft real-time applications. The success of Erlang is witnessed by the increasing number of its industrial applications. For instance, Erlang has been used to implement Facebook’s chat back-end, the mobile application Whatsapp or Twitterfall—a service to view trends and patterns from Twitter—, to name a few. The success of the language, however, also requires the development of powerful testing and verification techniques. Symbolic execution is at the core of many program analysis and transformation techniques, like partial evaluation, test-case generation or model checking. In this paper, we introduce a symbolic execution technique for Erlang. We discuss how both an overapproximation and an underapproximation of the concrete semantics can be obtained. We illustrate our approach through some examples. To the best of our knowledge, this is the first attempt to formalize symbolic execution in the context of this language, where previous approaches have only considered exploring different schedulings but have not dealt with symbolic data. More details can be found in the companion technical report