Crafter.Build/examples/wasi/README.md

# WASI

Build a C++26 program for the `wasm32-wasi` target and run it in a browser.

## Prerequisites

- A WASI sysroot with the exception-enabled libc++, `lib/wasm32-wasip1/eh/`
  from wasi-sdk 33 or later: wasm builds compile C++ exceptions and link those
  libraries. The Flatpak bundles one, which `crafter-build` uses as it is.
  Elsewhere, point `CRAFTER_BUILD_WASI_SYSROOT` at a wasi-sdk sysroot, or set
  `cfg.sysroot` in `project.cpp`. Arch's `wasi-libc++` packages have no such
  libraries, and the build stops with a message saying so.
- For the browser: WebAssembly exception handling, in Chrome 137, Firefox 131,
  Safari 18.4 or newer.

## Build

```bash
crafter-build
```

Output lands in `bin/wasi-hello-wasm32-wasip1-native/`:

- `wasi-hello.wasm` — the compiled module
- `index.html` + `runtime.js` — a minimal in-browser WASI shim, dropped in by
  `EnableWasiBrowserRuntime(cfg)` in `project.cpp`. Stdout goes to the browser
  console.

## Run in a browser

```bash
./serve.sh                  # any static file server works
```

Open `http://localhost:8080/`. The string from `main()` shows up in the
DevTools console.

## Run in a standalone runtime

If you don't need the browser, drop the `EnableWasiBrowserRuntime(cfg)` line
from `project.cpp` and run the `.wasm` directly:

```bash
wasmtime bin/wasi-hello-wasm32-wasip1-native/wasi-hello.wasm
```