CODEWITHSUNDEEP
javascriptwebassemblyzig
Challenger5
Challenger5

Reputation: 1064

Errors with compiling Zig to wasm32-freestanding

I am trying to compile Zig functions to a freestanding WebAssembly module using the wasm32-freestanding target. The official documentation has a section explaining how to do this, but with a recent version of Zig (0.8.0) I get errors when trying to instantiate the resulting module with JavaScript.

// file: main.zig
export fn add(a: i32, b: i32) i32 {
    return a +% b;
}

// file: test.js
WebAssembly.instantiate((function() {
    const source = require("fs").readFileSync("main.o");
    return new Uint8Array(source);
})(), { env: {} }).then(wasm => {
    const add = wasm.instance.exports.add;
    console.log(add(1, 2));
});

$ zig version
0.8.0
$ node --version
14.17.3
$ zig build-obj main.zig -target wasm32-freestanding -dynamic -OReleaseFast
$ wc -c main.o # the generated code has extension `.o` instead of `.wasm`
135
$ node test.js
(node:2449) UnhandledPromiseRejectionWarning: LinkError: WebAssembly.instantiate(): Import #0 module="env" function="__linear_memory" error: memory import must be a WebAssembly.Memory object
(Use `node --trace-warnings ...` to show where the warning was created)
(node:2449) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:2449) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Inspecting the generated wasm module shows that it attempts to import a value called __linear_memory from the scope env. Naturally this fails as I am not providing such an import. However, the example project zig-wasm-test includes a WASM module (compiled with an old version of Zig) which does not include these imports.

What am I doing wrong here? Should I just be providing a __linear_memory export to the module even though it isn't used?

Upvotes: 1

Views: 924

Answers (1)

kristoff
kristoff

Reputation: 652

You should try using build-lib instead of build-obj.

Upvotes: 2

Related Questions