Safe, shared-memory interoperability between languageswith different type systems and memory-safety guarantees is an intricate problem as crossing language boundaries may result in memory-safety violations. In this paper, we present RichWasm, a novel richly typed intermediate language designed to serve as a compilation target for typed high-level languages with different memory-safety guarantees. RichWasm is based on WebAssemblyand enables safe shared-memory interoperability by incorporating a variety of type features that support fine-grained memory ownership and sharing. RichWasm is rich enough to serve as a typed compilation target for both typed garbage-collected languages and languages with an ownership-based type system and manually managed memory. We demonstrate this by providing compilers from core ML and L 3 , a type-safe language with strong updates, to RichWasm. RichWasm is compiled to regular Wasm, allowing for use in existing environments. We formalize RichWasm in Coq and prove type safety.

Summary In recent work, Lemire (2021) presented a fast algorithm to convert number strings into binary floating‐point numbers. The algorithm has been adopted by several important systems: for example, it is part of the runtime libraries of GCC 12, Rust 1.55, and Go 1.16. The algorithm parses any number string with a significand containing no more than 19 digits into an IEEE floating‐point number. However, there is a check leading to a fallback function to ensure correctness. This fallback function is never called in practice. We prove that the fallback is unnecessary. Thus we can slightly simplify the algorithm and its implementation.

Programs are rarely implemented in a single language, and thus questions of type soundness should address not only the semantics of a single language, but how it interacts with others. Even between type-safe languages, disparate features can frustrate interoperability, as invariants from one language can easily be violated in the other. In their seminal 2007 paper, Matthews and Findler proposed a multi-language construction that augments the interoperating languages with a pair of boundaries that allow code from one language to be embedded in the other. While this technique has been widely applied, their syntactic source-level interoperability doesn’t reflect practical implementations, where the behavior of interaction is only defined after compilation to a common target, and any safety must be ensured by target invariants or inserted target-level “glue code.”