Automatic Inference of Class Invariants

Abstract

We present a generic framework for the automatic and modular inference of sound class invariants for class-based object oriented languages. The idea is to derive a sound class invariant as a conservative abstraction of the class semantics. In particular we show how a class invariant can be characterized as the solution of a set of equations extracted from the program source. Once a static analysis for the method bodies is supplied, a solution for the former equation system can be iteratively computed. Thus, the class invariant can be automatically inferred. Moreover, our framework is modular since it allows the derivation of class invariants without any hypothesis on the instantiation context and, in the case of subclassing, without accessing to the parent code.