Verification of Programs with Exceptions Through Operator Precedence Automata

Abstract

Operator Precedence Languages are one of the most expressive classes of context-free languages that enable Model Checking. Recently, the First-Order complete Precedence Oriented Temporal Logic (POTL) has been introduced for expressing properties on models defined through Operator Precedence Automata (OPA), a variant of Pushdown Automata for OPLs; moreover, an efficient tool called Precedence Oriented Model Checker (POMC) was devised for POTL. We propose here the core algorithms of POMC for on-the-fly depth-first exploration of the search space: for OPA, a reachability algorithm; for their ω-word variant, a fair-cycle detection algorithm. We have refined the tool with a user-friendly DSL called MiniProc for expressing procedural code with exceptions. We show how the expressiveness of POMC can be used to verify programs which make use of exceptions, thus overcoming the limits of LTL-based Model Checking. We demonstrate the effectiveness of POMC through a case study.