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vados-cosmonic merged 1 commit into from
Jul 23, 2025
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feat(lang/c): use wasm32-wasip2-clang binary directly #289

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33 changes: 28 additions & 5 deletions component-model/src/language-support/c.md
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Original file line number Diff line number Diff line change
Expand Up @@ -53,9 +53,30 @@ uint32_t exports_docs_adder_add_add(uint32_t x, uint32_t y)
}
```

## 4. Compile a WebAssembly module (P1) with `clang`
## 4. Compile a WebAssembly P2 component with `wasi-sdk`'s `wasm32-wasip2-clang`

Now, you can compile the function into a Wasm module via clang:
Given that `wasi-sdk` has ben installed, we can build a Preview 2 component quickly by using the provided `wasm32-wasip2-clang` binary:

```console
/opt/wasi-sdk/bin/wasm32-wasip2-clang \
-o adder.wasm \
-mexec-model=reactor \
component.c \
adder.c \
adder_component_type.o
```

After this command completes, you will have a new file named `adder.wasm` available in the source folder.

For use cases that require building a P1 module and/or adapting an existing P1 module into a P2 module,
such as buliding for a platform that does not support P2, details on a more manual approach can be found below:

<details>
<summary>Manual P1 & P2 build using `wasi-sdk`'s `clang` and `wasm-tools`</summary>

## Build a WebAssembly module (P1) with `clang`

Compile the component code into a WebAssembly P1 module via clang:

```console
clang component.c adder.c adder_component_type.o -o adder.wasm -mexec-model=reactor
Expand All @@ -77,7 +98,7 @@ clang component.c adder.c adder_component_type.o -o adder.wasm -mexec-model=reac
[wasi-sdk-images]: https://github.com/WebAssembly/wasi-sdk/pkgs/container/wasi-sdk
[wasi-sdk-dockerfile]: https://github.com/WebAssembly/wasi-sdk/blob/main/docker/Dockerfile

## 5. Convert the P1 component to a P2 component with `wasm-tools`
### Convert the P1 component to a P2 component with `wasm-tools`

Next, we need to transform the P1 component to a P2 component. To do this, we can use `wasm-tools component new`:

Expand All @@ -88,7 +109,7 @@ wasm-tools component new ./adder.wasm -o adder.component.wasm
> [!NOTE]
> The `.component.` extension has no special meaning -- `.wasm` files can be either modules or components.

## 6. (optional) Build a WASI-enabled WebAssembly (P2) component with `wasm-tools`
### (optional) Build a WASI-enabled WebAssembly (P2) component with `wasm-tools`

Do note `wasm-tools component new` may fail if your code references any [WASI][wasi] APIs that must be imported, for
example via standard library imports like `stdio.h`.
Expand Down Expand Up @@ -135,7 +156,9 @@ wasm-tools component new adder.wasm --adapt wasi_snapshot_preview1.wasm -o adder

[wasmtime-releases]: https://github.com/bytecodealliance/wasmtime/releases

## 7. Inspect the built component
</details>

## 5. Inspect the built component

Finally, you can inspect the embedded wit to see your component (including any WASI imports if necessary):

Expand Down