wasm-opt is a component of the Binaryen toolkit that optimizes WebAssembly modules. It is written in C++.

This project provides a Rust crate that builds wasm-opt and:

1. makes its command-line interface installable via cargo install,
2. provides an API to access it programmatically.

cargo install wasm-opt --locked

It should behave exactly the same as wasm-opt installed from other sources.

See the API documentation.

git clone https://github.com/brson/wasm-opt-rs
cd wasm-opt-rs
git submodule update --init --recursive
cargo build && cargo test

Requires Rust 1.48+ and a C++ compiler with C++17 support. It does not require CMake or other C++ build tools.

These are the earliest C++ compiler versions known to work:

• gcc 7
• clang 7
• Visual Studio 2019

• The wasm-opt-sys crate takes a non-negligible amount of time to build. It also does not do any incremental recompilation, so if the build is invalidated it will rebuild the C++ code from scratch. The lack of incremental recompilation is a limitation self-imposed by not using cmake or other external build system.
• wasm-opt on Windows does not support extended unicode paths (probably anything non-ASCII). This is a limitation of binaryen and not a regression of the bindings. It may or may not be fixed in the future. The APIs will return an error if this occurs.
• cargo tarpaulin (code coverage) segfaults running any wasm-opt crates, reason unknown. This behavior could infect other crates that link to wasm-opt. If you use tarpaulin, you might verify it continues to work.

Binaryen uses a single monotonically-increasing number for versions. This crate uses the semver minor version to track the Binaryen version, so e.g. the wasm-opt crate version 0.110.0 corresponds to Binaryen 110. Point releases are used for bugfixes.

Since minor version bumps of crates earlier than 1.0.0 are considered breaking, users need to explicitly upgrade versions of wasm-opt to get new Binaryen releases, and upgrades may have breaking API changes, though we don't anticipate significant changes.

This project was created thanks to a grant from the Web3 Foundation.

Licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Binaryen itself, code from which is compiled and linked by this project, is licensed under the terms of the Apache License, Version 2.0.