Wastrel, a Profligate Implementation of WebAssembly

6 months ago

Wastrel is a new WebAssembly (Wasm) implementation that compiles Wasm modules to standalone binaries by emitting C and then compiling that C.
Key differences from similar projects (wasm2c, w2c2) include aiming to support automatic memory management via WasmGC using the Whippet garbage collection library.
Wastrel's CLI resembles wasmtime, compiling and running the C output by default, unlike wasm2c which focuses on C production.
Implements WASI 0.1 (WASI preview 1), allowing direct execution of binaries using WASI imports.
Emits optimized C code with a lightweight effects analysis to minimize useless temporaries.
Performance benchmarks show Wastrel is 2-5% slower than native, comparable to w2c2, and significantly faster than Wasmtime.
Implementing WASI was challenging due to the need to handle ABIs with limited types, the complexity of WASI functions like poll_oneoff, and underspecification issues.
Uses Linux's filesystem namespaces for secure sandboxing, making it Linux-only and emphasizing a capabilities-based approach.
Motivations include advocating for garbage collection in WASI, supporting WasmGC languages outside browsers, and promoting the Whippet GC library.
Future goals include exploring performance against ocamlopt and enabling native compilation of Guile programs via Hoot, Whippet, and Wastrel.

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