So I create some UserScripts as a hobby for a game and have been looking to write some of them in Rust and compile them down to wasm, but I have noticed that what outputted .wasm binary file is different based off the OS that is building it.

I created a little repo to try and test exactly where it is, using my MacOS builds and GitHub actions for a Ubuntu build. Both running the same version of rustc.

> rustc --version
rustc 1.75.0-nightly (4b85902b4 2023-11-04)

info: syncing channel updates for 'nightly-x86_64-unknown-linux-gnu'
info: latest update on 2023-11-05, rust version 1.75.0-nightly (4b85902b4 2023-11-04)

The program I am testing with is a simple app that prints 'Hello, world!'.

fn main() {
    println!("Hello, world!");
}

The first test I did was using rustc itself to build the .wasm binaries and did manage to get identical outputs across MacOS and Ubuntu

rustc --target=wasm32-unknown-unknown main.rs

The second test I did was switching to using Cargo instead and found that it was now producing different outputs across MacOS and Ubuntu for the same code.

cargo build --release --target=wasm32-unknown-unknown

I don't know why its not being deterministic when I used cargo over rustc as the flags I passed to either on both OS' are identical with the same versions of rustc. You can see the entire repo here. Any help would be appreciated.