Expression-Based Aliasing for OO–languages

Abstract

Alias analysis has been an interesting research topic in verification and optimization of programs. The undecidability of determining whether two expressions in a program may reference to the same object is the main source of the challenges raised in alias analysis. In this paper 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 in the $\mathbb {K}$-framework. An important property of our extension is that, in a non-concurrent setting, the corresponding alias expressions can be over-approximated in terms of a notion of regular expressions. This further enables us to show that the associated $\mathbb {K}$-machinery implements 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. As a case study, we analyze the integration and further applications of the alias calculus in SCOOP. The latter is an object-oriented programming model for concurrency, recently formalized in Maude; $\mathbb {K}$ definitions can be compiled into Maude for execution.