Jorijn van der Graaf
3e125d83f0
The README called an exception escaping main a trap. It is an uncaught WebAssembly exception, and nothing prints its type or what(); the README says so now. It also lists what a wasm build refuses and why, says that setjmp needs -lsetjmp and that a longjmp across a noexcept function ends the program, that a wasmtime older than 47 needs -W exceptions=y, and that an old wasm-opt on PATH breaks release links. It documents exit and park in a page from EnableWasiBrowserRuntime, with the declaration of the park import. The wasi example still sent Arch users to wasi-libc++, which has no exception-enabled libraries. It asks for a wasi-sdk 33 sysroot or the Flatpak now, and names the browsers a page needs. AGENTS.md notes that the runtime test needs node, so it runs in the native loop and not in CI. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
45 lines
1.3 KiB
Markdown
45 lines
1.3 KiB
Markdown
# WASI
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Build a C++26 program for the `wasm32-wasi` target and run it in a browser.
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## Prerequisites
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- A WASI sysroot with the exception-enabled libc++, `lib/wasm32-wasip1/eh/`
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from wasi-sdk 33 or later: wasm builds compile C++ exceptions and link those
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libraries. The Flatpak bundles one, which `crafter-build` uses as it is.
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Elsewhere, point `CRAFTER_BUILD_WASI_SYSROOT` at a wasi-sdk sysroot, or set
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`cfg.sysroot` in `project.cpp`. Arch's `wasi-libc++` packages have no such
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libraries, and the build stops with a message saying so.
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- For the browser: WebAssembly exception handling, in Chrome 137, Firefox 131,
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Safari 18.4 or newer.
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## Build
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```bash
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crafter-build
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```
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Output lands in `bin/wasi-hello-wasm32-wasip1-native/`:
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- `wasi-hello.wasm` — the compiled module
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- `index.html` + `runtime.js` — a minimal in-browser WASI shim, dropped in by
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`EnableWasiBrowserRuntime(cfg)` in `project.cpp`. Stdout goes to the browser
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console.
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## Run in a browser
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```bash
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./serve.sh # any static file server works
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```
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Open `http://localhost:8080/`. The string from `main()` shows up in the
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DevTools console.
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## Run in a standalone runtime
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If you don't need the browser, drop the `EnableWasiBrowserRuntime(cfg)` line
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from `project.cpp` and run the `.wasm` directly:
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```bash
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wasmtime bin/wasi-hello-wasm32-wasip1-native/wasi-hello.wasm
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```
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