Bindgen and rustwasmc

The rustwasmc tool is inspired by the wasm-pack project but is optimized for edge cloud and device applications. Specifically, it supports the WasmEdge WebAssembly runtime.

One of the key features of rustwasmc over the standard wasm32-wasi compiler target is that rustwasmc processes compiled Rust functions using the wasm-bindgen tool. By default, WebAssembly functions only support a few simple data types as input call arguments. Tools like wasm-bindgen turn WebAssembly function arguments into memory pointers, and allow host applications to pass complex arguments, such as strings and arrays, to WebAssembly functions. WasmEdge's Node.js SDK and Go SDK both support wasm-bindgen, allowing JavaScript and Go programs to call WebAssembly function with complex call arguments.

At this time, we require Rust compiler version 1.50 or less in order for WebAssembly functions to work with wasm-bindgen and rustwasmc. We will catch up to the latest Rust compiler version once the Interface Types spec is finalized and supported.


The rustwasmc depends on the Rust cargo toolchain to compile Rust source code to WebAssembly. You must have Rust installed on your machine.

$ curl --proto '=https' --tlsv1.2 -sSf | sh
$ source $HOME/.cargo/env
$ rustup override set 1.50.0


The easiest way to install rustwasmc is to use its installer.

$ curl -sSf | sh

Alternatively, you can install using the NPM if you'd like.


To build Rust functions for Node.js applications, use the following command. See a template application.

$ rustwasmc build

Use the --enable-ext flag to compile Rust programs that use WASI extensions, such as WasmEdge's storage and Tensorflow APIs. The rustwasmc will generates the compiled WebAssembly bytecode program for the wasmedge-extensions Node.js module instead of the wasmedge-core module in this case.

$ rustwasmc build --enable-ext

Support AOT

A key feature of the WasmEdge runtime is its support for Ahead-of-Time (AOT) compilers. When you run WebAssembly programs in Node.js wasmedge-core and wasmedge-extensions add-ons, you typically do not need to worry about it as the add-on handles AOT compilation transparently. However, in some cases, you do want the rustwasmc to compile and generate native code for the program.

Then, use the commands below to bring your operating system up to date with the latest developer tools. The commands here are tested on Ubuntu 20.04.

$ sudo apt-get update
$ sudo apt-get -y upgrade
$ sudo apt install build-essential curl wget git vim libboost-all-dev llvm-dev liblld-10-dev

Now, you can build the .so files for the AOT native target like the following.

$ rustwasmc build --enable-aot

Enjoy coding!