Side effect monitoring for Java using bytecode rewriting

Abstract

A side effect of a method in Java is a read or write operation that the method may perform on an object in the heap. Methods with side effects are more difficult to understand and to reason about than pure methods, in particular in the presence of aliasing. While both, Java and the underlying Java Virtual Machine (JVM), support specifying and checking types statically, neither supports ways of specifying and checking side effects statically or at run time.We propose a technique to specify the side effects of a method and to perform fine-grained monitoring of its side effects at run time. It relies on a domain specific contract language to specify sets of memory locations, assign read and write permissions to them, and enforce these permissions during portions of a program's execution.We present a specification and an implementation of our monitoring technique.The implementation works independently of any particular JVM by employing bytecode rewriting. The implementation ensures complete interposition while supporting all languages and language features that run on a standard JVM. We evaluate the implementation on a set of benchmarks.