Unable to instantiate logger due to error message which originates from wasm-bindgen

[lexi-the-cute]

Summary

When running console_log::init().unwrap(); from the below code, I get the error message: function not implemented on non-wasm32 targets on Firefox.

if cfg!(any(target_arch = "wasm32", target_arch = "wasm64")) {
    console_log::init().unwrap();
}

Additional Details

The build script is really complicated right now. I currently call SDL_main as I have not been able to get any indication of the code running in console if I attached the wasm_bindgen macro at all.

// Run as Library (e.g. Android and WebAssembly)
#[no_mangle]
#[allow(non_snake_case)]
pub extern fn SDL_main(_argc: libc::c_int, _argv: *const *const libc::c_char) -> libc::c_int {
    game::start();
    return 0;
}

I'm using:

console_log = { version = "1.0.0", features = ["color", "wasm-bindgen"] }
wasm-bindgen = "0.2.86"

I'm calling my wasm file with the below code after I generate both the js and wasm file with emmc:

<script type="text/javascript">
var Module = {
    onRuntimeInitialized: function() {
        Module._SDL_main(); // SDL_main was exported
    }
};
</script>
<script src="/main.js"></script>

My project is located at https://github.com/alexisart/catgirl-engine

[daxpedda]

if cfg!(any(target_arch = "wasm32", target_arch = "wasm64")) {

FWIW this can be shortened with target_family = "wasm".

[..] I get the error message: function not implemented on non-wasm32 targets [..]

There's really very little info to go by here. But I'm going to assume that the issue here is the compile target. wasm-bindgen officially only supports wasm32-unknown-unknown, you might have tried a different target. Looking at your repo, did you maybe try to use Emscripten?

It would be really helpful to put up a minimal reproducible example.

[lexi-the-cute]

Here's the minimal reproducible example

min.zip

[daxpedda]

You seem to be compiling with --target wasm32-unknown-emscripten, which is not supported in wasm-bindgen. Unfortunately I know nothing about Emscripten so I can't really give you further advice on your project.

By the way, the .cargo/config.toml.sample file doesn't need to be copied to your home folder. Using a local .cargo/config.toml (removing .sample at the end) works too and should have the same effect locally without having to change your global configuration. See the Cargo book for more information.

[lexi-the-cute]

Okay, so I was trying to remove wasm-bindgen from my project, but it refused to do it. It turns out that the console-log crate depends on wasm-bindgen.

I'm going to reimplement the logger from scratch because I need proper logging to work and I can't use wasm32-unknown-unknown due to other dependencies banning using unknown target OS and requiring specifying using an "OS" even if it's emscripten.

I would like to reopen this issue as a feature request to start supporting emscripten

[daxpedda]

Unfortunately that's not possible, as wasm-bindgen considers Emscripten to be out of scope.

The deeper problem here is that wasm32-unknown-unknown isn't compatible with the C ABI: rust-lang/rust#71871. This is a common problem that appears when wanting to use wasm-bindgen: #2317.

Unfortunately there is currently no solution for this, though the Rust team is aware of it and is trying to find a solution: rustwasm/team#291. One proposal that might solve that problem is a new Wasm ABI: rust-lang/rust#83788. Though it is currently still unstable.

So as it stands today, wasm-bindgen is not compatible with C, you will either have to drop wasm-bindgen or C to proceed.

[lexi-the-cute]

Thanks! I dropped wasm-bindgen as I wasn't using it myself, it was just a dependency of one of my dependencies. I've successfully implemented my own logger by using Emscripten's EM_ASM. This requires writing both very basic C and continuing Rust as usual, but it at least works.