A core Erlang semantics for declarative debugging

Abstract

One of the main advantages of declarative languages is their clearly established formal semantics, that allows programmers to reason about the properties of programs and to establish the correctness of tools. In particular, declarative debugging is a technique that analyses the proof trees of computations to locate bugs in programs. However, in the case of commercial declarative languages such as the functional language Erlang, sometimes the semantics is only informally defined, and this precludes these possibilities. Moreover, defining semantics for these languages is far from trivial because they include complex features needed in real applications, such as concurrency. In this paper we define a semantics for Core Erlang, the intermediate language underlying Erlang programs. We focus on the problem of concurrency and show how a medium-sized-step calculus, that avoids the details of small-step semantics but still captures the most common program errors, can be used to define an algorithmic debugger that is sound and complete.