Implementing Garbage Collection for Active Objects on Top of Erlang

Abstract

ABS is a language for modeling and simulating distributed systems. ABS has been in development at the University of Oslo for a number of years and has been the technical underpinning for a number of national and EU-wide research projects such as HATS and Envisage. The key characteristic of ABS is a semantics of active objects encapsulating parallel behavior in a safe way. Objects communicate via asynchronous method calls and future variables. Modern programming languages typically relieve programmers of the burden of manually managing memory. Errors due to memory leaks and dangling pointers has been a headache in low-level languages like C. ABS has an Erlang back end that has been developed as part of a master s thesis by Georg Göri at the Graz University of Technology. Although Erlang is a garbage collected language, it cannot collect idle processes. In this thesis, a garbage collector that stops processes that represent active objects, future variables and schedulers in the Erlang back end, has been developed. The thesis discusses measures taken to ensure correct collection of these processes, as well as strategies employed to balance completeness and speed.