Garbage Collection for Rust: The Finalizer Frontier

Rust is a non-Garbage Collected (GCed) language, but the lack of GC makes expressing data-structures that require shared ownership awkward, inefficient, or both. In this paper we explore a new design for, and implementation of, GC in Rust, called Alloy. Unlike previous approaches to GC in Rust, Alloy maps existing Rust destructors to finalizers: this makes GC in Rust natural to use but introduces surprising soundness, performance, and ergonomic problems. Alloy provides solutions for each of these problems.