Formal Type Soundness for Cyclone’s Region System

Cyclone is a polymorphic, type-safe programming language derived from C. The primarydesign goals of Cyclone are to let programmers control data representations and memory man-agement without sacrificing type-safety. In this paper, we focus on the region-based memorymanagement of Cyclone and its static typing discipline. The design incorporates several advance-ments, including support for region subtyping and a coherent integration with stack allocationand a garbage collector. To support separate compilation, Cyclone requires programmers towrite some explicit region annotations, but uses a combination of default annotations, localtype inference, and a novel treatment of region effects to reduce this burden. As a result, weintegrate C idioms in a region-based framework. In our experience, porting legacy C to Cyclonehas required altering about 8% of the code; of the changes, only 6% (of the 8%) were regionannotations.This technical report is really two documents in one: The first part is a paper submittedfor publication in November, 2001. The second part is the full formal language and type-safetyproof mentioned briefly in the first part. If you have already read a version of, “Region-BasedMemory Management in Cyclone”, then you should proceed directly to Section 9.