Symbolic execution of concurrent objects in CLP

In the concurrent objects model, objects have conceptually dedicated processors and live in a distributed environment with unordered communication by means of asynchronous method calls. Method callers may decide at runtime when to synchronize with the reply from a call. This paper presents a CLP-based approach to symbolic execution of concurrent OO programs. Developing a symbolic execution engine for concurrent objects is challenging because it needs to combine the OO features of the language, concurrency and backtracking. Our approach consists in, first, transforming the OO program into an equivalent CLP program which contains calls to specific builtins that handle the concurrency model. The builtins are implemented in CLP and include primitives to handle asynchronous calls synchronization operations and scheduling policies, among others. Interestingly, symbolic execution of the transformed programs then relies simply on the standard sequential execution of CLP. We report on a prototype implementation within the PET system which shows the feasibility of our approach.