To study the properties of the Java Virtual Machine(JVM) and Java programs, our research group has produced a series of JVM models written in a functional subset of Common Lisp. In this paper, we present our most complete JVM model from this series, namely, M6, which is derived from a careful study of the J2ME KVM [16] implementation.On the one hand, our JVM model is a conventional machine emulator. M6 models accurately almost all aspects of the KVM implementation, including the dynamic class loading, class initialization and synchronization via monitors. It executes most J2ME Java programs that do not use any I/O or floating point operations. Engineers may consider M6 an implementation of the JVM. It is implemented with around 10K lines in 20+ modules.On the other hand, M6 is a novel model that allows for analytical reasoning besides conventional testing. M6 is written in an applicative (side-effect free) subset of Common Lisp, for which we have given precise meaning in terms of axioms and inference rules. A property of M6 can be expressed as a formula. Rules of interference can be used analytically to derive properties of M6 and the Java programs that run on the model, using a mechanical theorem prover.We argue that our approach of building an executable model of the system with an axiomatically described functional language can bring benefits from both the testing and the formal reasoning worlds.
展开▼
