[BUG] `af_set_backend` is declared with the wrong parameter width

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Assessment

Difficulty
1/5
Estimated time
Under an hour
Newbie friendliness
88/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
c, rust
Domain
backend

Research direction

Start in src/core/backend.rs:7 and compare af_set_backend with the neighboring declarations in the same extern block. Check include/af/backend.h:24 to confirm the C enum type, update the Rust declaration to match the ABI, then run the repository's Rust checks or tests. Done means the declaration uses the correct parameter width and the checks pass.

Written by the indexing model from the issue text.

Description

Bug

src/core/backend.rs:7:

extern "C" {
    fn af_set_backend(bknd: u8) -> c_int;

The C signature (include/af/backend.h:24) is:

AFAPI af_err af_set_backend(const af_backend bknd);

af_backend is a C enum, i.e. 4-byte int under both MSVC and GCC. Declaring the parameter as u8 is an ABI type mismatch.

In practice it works, because rustc emits zeroext for the u8 argument and the callee reads a clean value from the full register — I checked the IR (declare noundef i32 @af_set_backend(i8 noundef zeroext)). So this is as a latent correctness issue rather than an active bug, but it should still be c_uint to match the C ABI.

The three neighbouring declarations in the same extern block already use c_uint/c_int correctly.

Found by Claude Opus 5.

Dominant language
Rust
Stars
827
Forks
59
No merged PRs in 30d

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