Static WASM_C_ABI

pub static WASM_C_ABI: &Lint

The wasm_c_abi lint detects usage of the extern "C" ABI of wasm that is affected by a planned ABI change that has the goal of aligning Rust with the standard C ABI of this target.

Example

#[repr(C)]
struct MyType(i32, i32);

extern "C" my_fun(x: MyType) {}

This will produce:

error: this function function definition is affected by the wasm ABI transition: it passes an argument of non-scalar type `MyType`
--> $DIR/wasm_c_abi_transition.rs:17:1
 |
 | pub extern "C" fn my_fun(_x: MyType) {}
 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 |
 = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
 = note: for more information, see issue #138762 <https://github.com/rust-lang/rust/issues/138762>
 = help: the "C" ABI Rust uses on wasm32-unknown-unknown will change to align with the standard "C" ABI for this target

Explanation

Rust has historically implemented a non-spec-compliant C ABI on wasm32-unknown-unknown. This has caused incompatibilities with other compilers and Wasm targets. In a future version of Rust, this will be fixed, and therefore code relying on the non-spec-compliant C ABI will stop functioning.