# Cross-crate error-ID final-link checks

From the repository root, run `nix develop -c make -C firmware native-test`.
For a separate artifact directory:

```sh
nix develop -c env CARGO_BUILD_JOBS=2 python3 firmware/libs/kaptan-err-reportable-macros/tests/final_link.py \
  --work-dir /tmp/kaptan-final-link
```

The fixture builds two crates using the production `KaptanError` derive as
rlibs and staticlibs. Rust and C++ executables cover unique and duplicate IDs,
used and unused error values, and an unused second crate. Successful executables
must run. Expected duplicate failures must name `__kaptan_error_id_65401`.

The helper seeds its fixture lock from `firmware/Cargo.lock`, verifies registry
versions, sources and checksums, then builds with Rust 1.90.0 and `--locked
--offline`. It retains source, manifests, locks, binaries, linker output and
`results.txt` with the Rust compiler identity and all twelve outcomes. Native linker flags
are Linux-specific.

The exported `#[used]` marker detects collisions when both defining objects
participate in the link. It cannot force extraction of an unreferenced staticlib
member. The native case that calls only the first crate can therefore link despite
the duplicate ID. Rust's release-LTO fixture explicitly names the second crate
and rejects that collision. These cases do not establish catalog-wide uniqueness
across every supplied archive or every embedded linker/LTO combination. Stable
error-ID allocation still requires review.