Custom build.rs cannot find a dependency

[4JX]

Having some trouble with adding gtk related dependencies to my repo (flake here)

Running nix run . -L -- gives

error: builder for '/nix/store/vncyapz464vqiz2s362q0m25k15l62r5-legion-kb-rgb-0.19.0.drv' failed with exit code 101;
       last 10 log lines:
       > ++ command cargo build --release --message-format json-render-diagnostics --locked
       >    Compiling legion-kb-rgb v0.19.0 (/build/source/app)
       >    Compiling legion-rgb-driver v0.1.0 (/build/source/driver)
       > error: failed to run custom build command for `legion-kb-rgb v0.19.0 (/build/source/app)`
       > note: To improve backtraces for build dependencies, set the CARGO_PROFILE_RELEASE_BUILD_OVERRIDE_DEBUG=true environment variable to enable debug information generation.
       >
       > Caused by:
       >   process didn't exit successfully: `/build/source/target/release/build/legion-kb-rgb-571b2982fa2eefd1/build-script-build` (exit status: 127)
       >   --- stderr
       >   /build/source/target/release/build/legion-kb-rgb-571b2982fa2eefd1/build-script-build: error while loading shared libraries: libgobject-2.0.so.0: cannot open shared object file: No such file or directory
       For full logs, run 'nix log /nix/store/vncyapz464vqiz2s362q0m25k15l62r5-legion-kb-rgb-0.19.0.drv'.
error: 1 dependencies of derivation '/nix/store/5ffy9w745qkhydz6bg3c2yscqb0hl0l7-legion-kb-rgb.drv' failed to build

Tried adding gobject-introspection to buildInputs (what I assumed would work) and then glib for redundancy (which seems to contain the lib if queried with nix-index -c nix-locate --top-level libgobject-2.0) but neither worked. Doesn't feel like this is specifically an issue with crane itself, but I'm really not sure why its not picking up on the lib's existence.

[ipetkov]

You may be missing a nativeBuildInputs = [ pkgs.pkg-config ];? pkg-config is the standard way of having different build scripts find out about where particular libraries are (which is especially important for building with Nix since those libraries won't be at /usr/lib or equivalent

[4JX]

Wouldn't seem like it as I already do have that.

[ipetkov]

Hmm I'm not entirely sure then. I would investigate how the build script (or rather the crate it delegates to) is looking for libraries and how to nudge that in the right direction

[dpc]

Are you maybe using mold with a wrapper?

[4JX]

mold is used through adding a few env vars

MOLD_PATH = "${pkgs.mold.out}/bin/mold";
RUSTFLAGS = "-Clink-arg=-fuse-ld=${MOLD_PATH} -Clinker=clang";
LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";

And pkgs.mold just pulls and builds from source.

Or are you referring to using mold in any form?

[dpc]

https://github.com/fedimint/fedimint/pull/3228/files

[4JX]

Good lead, landed upon fixing it by removing the manual mold setup vars and instead using stdenv = pkgs.stdenvAdapters.useMoldLinker pkgs.stdenv in the dependency and main package derivations.

[dpc]

BTW. There's a PR NixOS/nixpkgs#257158 to nixpkgs to make using wrapped mold easier, which should benefit Rust users in particular.