A Verifier for Region-Annotated Java Bytecodes

This paper presents a verifier for the memory-safe execution of extended Java bytecodes that support region-based memory management and explicit deallocation primitives. The verifier reads in region-annotated bytecodes that augment the standard Java bytecodes with instructions for creating and removing memory regions, allocating objects in regions, and passing regions as parameters. The verification ensures that each region is live when objects in the region are in use and that the program does not follow dangling references. The verifier requires region-safety certificates to be provided along with the bytecodes. The verification process consists of a load-time verification of method bodies, and a lazy linkage verification of method calls. Our region system supports both regions that are not lexically scoped and dangling pointers; the verifier proposed in this paper can successfully handle both of these features. Our experiments indicate that the sizes of certificates are acceptable in practice, and that region verification incurs little run-time overhead.