We are using cbindgen 0.15.0 to auto generate our C bindings. Install the tool via:
cargo install --version 0.15.0 --force cbindgen
Generate a Cargo.toml for wlan-mlme-c by following the instructions on fuchsia.dev for the build target //src/connectivity/wlan/lib/mlme/rust/c-binding:wlan-mlme-c. As of this writing, this is done in the following way.
fx set PRODUCT.BOARD --cargo-toml-gen <other fx args> fx build build/rust:cargo_toml_gen fx gen-cargo //src/connectivity/wlan/lib/mlme/rust/c-binding:_wlan_mlme_c_rustc_static
cbindgen $FUCHSIA_DIR/src/connectivity/wlan/lib/mlme/rust/c-binding/ -o $FUCHSIA_DIR/src/connectivity/wlan/lib/mlme/rust/c-binding/bindings.h
At present, cbindgen changes the comment on the final line to use a /* */ style comment for the header guard. This is not recognized by fx format-code. Change the final line of bindings.h to be the following.
#endif // SRC_CONNECTIVITY_WLAN_LIB_MLME_RUST_C_BINDING_BINDINGS_H_
And finally, run fx format-code and check-in the new bindings.h
fx format-code --files=$FUCHSIA_DIR/src/connectivity/wlan/lib/mlme/rust/c-binding/bindings.h git add $FUCHSIA_DIR/src/connectivity/wlan/lib/mlme/rust/c-binding/bindings.h
cbindgen fails when running cargo metadata: Remove the Cargo.toml and Cargo.lock files from wlan-mlme-c folder and re-run fx gen-cargo ..
ERROR: Parsing crate wlan_mlme_c: can't find dependency version for xyz: Rebuild Fuchsia and re-run fx gen-cargo .
A binding is not generated: Run cbindgen with -v argument to get a better understand what types and functions were found and if they've been rejected.
Error message
cbindgen: error while loading shared libraries: libproc_macro-7924135655fecacc.so: cannot open shared object file: No such file or directory
Make sure rustc is the latest version by checking rustc --version. rustc 1.47.0-nightly (e5e33ebd2 2020-08-11) is known to work with cbindgen 0.15.0. If they become out of sync in some cases, try the latest version that is usually within the same day by running:
rustup update rustup default nightly