Copenhagen Programming Language Seminar
In previous work, Hallenberg et al.  have integrated region-based
memory management with a Cheney-style copying garbage collection
algorithm. In this talk, we prove the safety of the integration,
which relies on a refinement of the region typing rules that forbid
dangling pointers during evaluation.
To accommodate the triggering of garbage collection at any step in
the evaluation process, we base our type-safety result for the
region-based system on a small-step contextual semantics and show
that whenever a well-typed expression reduces to another expression,
possibly by deallocating a region, then no dangling pointers are
introduced. Because there are no dangling pointers in the initial
heap, no dangling pointers appears during evaluation.
The memory discipline, which combines garbage collection and
region-based memory management, is implemented for Standard ML in the
ML Kit compiler. Although in principle the refinement of the region
typing rules lead to less flexibility and can cause worse memory
behaviour than when dangling pointers are permitted, experiments show
that for a range of benchmark programs, the refinement has little
effect on the overall memory behaviour.
 Niels Hallenberg, Martin Elsman, and Mads Tofte. Combining Region Inference and Garbage Collection. In ACM SIGPLAN 2002 Conference on Programming Language Design and Implementation (PLDI'02). Berlin, Germany. June 2002.
Peter Sestoft. Administrative host: Camilla Jørgensen. All are welcome.
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