diff --git a/posts/2024-11-26-wasip2-tier-2.md b/posts/2024-11-26-wasip2-tier-2.md new file mode 100644 index 000000000..5c88dbb24 --- /dev/null +++ b/posts/2024-11-26-wasip2-tier-2.md @@ -0,0 +1,99 @@ +--- +layout: post +title: "The wasm32-wasip2 Target Has Reached Tier 2 Support" +author: Yosh Wuyts +--- + +## Introduction + +In April of this year we posted an update about [Rust's WASI +targets](https://blog.rust-lang.org/2024/04/09/updates-to-rusts-wasi-targets.html) +to the main Rust blog. In it we covered the rename of the `wasm32-wasi` target +to `wasm32-wasip1`, and the introduction of the new `wasm32-wasip2` target as a +"tier 3" target. This meant that while the target was available as part of +`rust-lang/rustc`, it was not guaranteed to build. We're pleased to announce +that this has changed in Rust 1.82. + +For those unfamiliar with WebAssembly (Wasm) components and WASI 0.2, here is a quick, simplified primer: + +- **Wasm** is a (virtual) instruction format for programs to be compiled into (think: x86). +- **Wasm Components** are a container format and type system that wrap Core Wasm instructions into typed, hermetic binaries and libraries (think: ELF). +- **WASI** is a reserved namespace for a collection of standardized Wasm component interfaces (think: POSIX header files). + +For a more detailed explanation see the [WASI 0.2 announcement post](https://bytecodealliance.org/articles/WASI-0.2) on the Bytecode Alliance blog. + +## What's new? + +Starting Rust 1.82 (2024-10-17) the `wasm32-wasip2` (WASI 0.2) target has +reached tier-2 platform support in the Rust compiler. Among other things this +now means it is guaranteed to build, and is now available to install via Rustup +using the following command: + +```bash +rustup target add wasm32-wasip2 +``` + +Up until now Rust users writing [Wasm +Components](https://component-model.bytecodealliance.org) would always have to rely on tools (such as +[cargo-component]) which target the WASI 0.1 target (`wasm32-wasip1`) and +package it into a WASI 0.2 Component via a post-processing step invoked. Now +that `wasm32-wasip2` is available to everyone via Rustup, tooling can +begin to directly target WASI 0.2 without the need for additional post-processing. + +What this also means is that ecosystem crates can begin targeting WASI 0.2 +directly for platform-specific code. WASI 0.1 did not have support for sockets. +Now that we have a stable tier 2 platform available, crate authors should be +able to finally start writing WASI-compatible network code. To target WASI 0.2 +from Rust, authors can use the following `cfg` attribute: + +[cargo-component]: https://github.com/bytecodealliance/cargo-component + +```rust +#[cfg(all(target_os = "wasi", target_env = "p2"))] +mod wasip2 { + // items go here +} +``` + +To target the older WASI 0.1 target, Rust also accepts `target_env = "p1"`. + +## Standard Library Support + +The WASI 0.2 Rust target reaching tier 2 platform support is in a way just the +beginning. means it's supported and stable. While the platform itself is now +stable, support in the stdlib for WASI 0.2 APIs is still limited. While the WASI +0.2 specification specifies APIs for example for timers, files, and sockets - if +you try and use the stdlib APIs for these today, you'll find they don't yet +work. + +We expect to gradually extend the Rust stdlib with support for WASI 0.2 APIs +throughout the remainder of this year into the next. That work has already +started, with +[rust-lang/rust#129638](https://github.com/rust-lang/rust/pull/129638) adding +native support for `std::net` in Rust 1.83. We expect more of these PRs to land +through the remainder of the year. + +Though this doesn't need to stop users from using WASI 0.2 today. The stdlib is +great because it provides *portable* abstractions, usually built on top of an +operating system's `libc` or equivalent. If you want to use WASI 0.2 APIs +directly today, you can either use the +[wasi](https://docs.rs/wasi/latest/wasi/) crate directly. Or generate your own +WASI bindings from the [WASI +specification's](https://github.com/WebAssembly/WASI/tree/main/wasip2) interface +types using [wit-bindgen](https://github.com/bytecodealliance/wit-bindgen/). + +## Conclusion + +The `wasm32-wasip2` target is now installable via Rustup. This makes it possible +for the Rust compiler to directly compile to the Wasm Components format +targeting the WASI 0.2 interfaces. There is now also a way for crates to compile +add WASI 0.2 platform support by writing: + +```rust +#[cfg(all(target_os = "wasi", target_env = "p2"))] +mod wasip2 {} +``` + +We're excited for Wasm Components and WASI 0.2 to have reached this milestone +within the Rust project, and are excited to see what folks in the community will +be building with it!