Region inference for an object-oriented language

Abstract

Region-based memory management offers several important potential advantages over garbage collection, including real-time performance, better data locality, and more efficient use of limited memory. Researchers have advocated the use of regions for functional, imperative, and object-oriented languages. Lexically scoped regions are now a core feature of the Real-Time Specification for Java (RTSJ) [5].Recent research in region-based programming for Java has focused on region checking, which requires manual effort to augment the program with region annotations. In this paper, we propose an automatic region inference system for a core subset of Java. To provide an inference method that is both precise and practical, we support classes and methods that are region-polymorphic, with regionpolymorphic recursion for methods. One challenging aspect is to ensure region safety in the presence of features such as class subtyping, method overriding, and downcast operations. Our region inference rules can handle these object-oriented features safely without creating dangling references.

Region inference for an object-oriented language

“…The normal type system for Core-Java can be derived from the region type checking system (given in a companion report [14]) by erasing all regionrelated notations. That is, if…”

“…The details are in our technical report [14]. The final dependency graph has the classes and methods organised into a hierarchy of strongly connected components (SCCs).…”

“…We have formalised a comprehensive set of region type checking rules and proven their safety properties in our technical report [14]. In our type system for regionannotated Core-Java, P ¡ def def denotes that class declaration def is well-region-typed (or well-typed in short), P R ¡ ¡ meth meth indicates that a method meth is well-typed, P R ¡ ¡ e t indicates that an expression e is well-typed, while ¡ P denotes that a region-annotated program P is well-typed.…”

“…It guarantees the existence of a well-region-typed target program P for each well-normal-typed source program P. By region erasure, we can show that both programs have the same observable behaviour (through bisimulation) in the absence of dangling accesses. The main safety property (proven in [14]) is that no dangling reference is ever created during the execution of any well-region-typed expression.…”

A Formal Soundness Proof of Region-Based Memory Management for Object-Oriented Paradigm

“…In our previous work [8], we have developed the first automatic region type inference system for object-oriented paradigm. Our compiler automatically augments unannotated object-oriented programs with regions type declarations and inserts region allocation/deallocation instructions that achieve a safe memory management.…”