Wasm-bindgen: Project won't compile with latest nightly release when `atomics+bulk-memory` are set

[d3lm]

Describe the Bug

I just stumbled upon the issue that the wasm-bindgen does not seem to be working with the latest nightly release if you pass rustc compiler flags for threading, e.g. rustflags=["-C", "target-feature=+atomics,+bulk-memory"].

This results in an obscure error that says

wasm-bindgen is currently incompatible with modules that already have a start function

I have found out that using an older nightly version fixes the issue. In my case I had to use nightly-2020-05-15 as new versions always told me that rustfmt for target 'x86_64-apple-darwin' is unavailable.

Steps to Reproduce

1. Create new project with wasm-pack new test
2. Run wasm-pack build with RUSTFLAGS='-C target-feature=+atomics,+bulk-memory'

Expected Behavior

I am not sure if this is a bug with the rust compiler itself or if it's an issue with wasm-bindgen, but I'd say that this should work very similar to older nightly versions such as nightly-2020-05-15.

[alexcrichton]

I think this was fixed very recently in https://github.com/rustwasm/wasm-bindgen/pull/2183, can y'all try that and see if it fixes things?

[azriel91]

Heya, I've tried it out and it works (I also ran into the same problem).

Steps to use repository version

1. Install wasm-bindgen-cli from repository

   git clone [email protected]:rustwasm/wasm-bindgen.git
   cd wasm-bindgen
   cargo install --path crates/cli -Z unstable-options --profile release --force
   

2. Patch your project to use the local repository copy:

   # Cargo.toml
   [patch.crates-io]
   wasm-bindgen = { path = "/path/to/rustwasm/wasm-bindgen" }
   

3. Build as normal.

[alexcrichton]

I'm going to close this since I believe it's fixed, but if it's still an issue let me know!