Emitting ES6 Module for `wasm32-unknown-emscripten`

bjorn3 · November 25, 2022, 8:32pm

WebAssembly ABI mismatch between clang and rust

opened 10:19AM - 04 May 20 UTC

A-ffi T-compiler O-wasm C-bug A-abi

When I compile this C code to `wasm32-wasi`: ```c typedef struct Vector { … int a; int b; } Vector; extern int extract_a(Vector v) { return v.a; } ``` And this Rust code to `wasm32-wasi`: ```rust #[repr(C)] struct Vector { a: i32, b: i32, } extern "C" { fn extract_a(v: Vector) -> i32; } fn main() { unsafe { extract_a(Vector { a: 5, b: 4 }); } } ``` And try link them together, I'm getting linking errors: ``` = note: lld: error: function signature mismatch: extract_a >>> defined as (i32, i32) -> i32 in /home/pierre/Projets/wasm-abi-test/target/wasm32-wasi/debug/deps/wasm_abi_test.67xpw7l331r9o5x.rcgu.o >>> defined as (i32) -> i32 in /home/pierre/Projets/wasm-abi-test/target/wasm32-wasi/debug/build/wasm-abi-test-9c49ce7f6c5ca031/out/libfoo.a(test.o) ``` It seems that, according to clang, passing a struct by value should inline the fields, while for Rust it should be passed by pointer. I uploaded an example project here: https://github.com/tomaka/wasm-abi-test It can be built with something like: > AR_wasm32_wasi=/path/to/wasi-sdk-10.0/bin/ar CC_wasm32_wasi=/path/to/wasi-sdk-10.0/bin/clang cargo run --target=wasm32-wasi Rust version: rustc 1.44.0-nightly (38114ff16 2020-03-21)

Note that only wasm32-unknown-unknown uses the wrong abi. wasm32-unknown-emscripten amd wasm32-wasi both use the correct C abi.

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Emitting ES6 Module for `wasm32-unknown-emscripten`

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