From c7dfeb21e58a1b79ec2f60f0955a4af37a749267 Mon Sep 17 00:00:00 2001
From: AlexBSoD <13933267+AlexBSoD@users.noreply.github.com>
Date: Wed, 29 Jul 2026 14:39:55 +0300
Subject: [PATCH] fix(nix): provide libclang in the dev shell
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Building any nRF firmware from `nix develop` fails in the build script of
nrf-mpsl-sys:

    Unable to find libclang: "couldn't find any valid shared libraries
    matching: ['libclang.so', ...], set the `LIBCLANG_PATH` environment
    variable to a path where one of these files can be found"

Both nrf-mpsl-sys and nrf-sdc-sys generate their bindings with bindgen, which
dlopens libclang at build time. The dev shell ships a full Rust toolchain and
the embedded tooling but never provided one, so every contributor had to dig a
clang out of the store and pass LIBCLANG_PATH by hand.

Point it at pkgs.llvmPackages.libclang. Verified by building keyboards/k04
central from a clean CARGO_TARGET_DIR inside `nix develop` with no manually
exported variables; nrf-mpsl-sys and nrf-sdc-sys both compile.

No BINDGEN_EXTRA_CLANG_ARGS is needed here — scripts/build_k04_matrix.sh still
derives its own when it wants ARM headers, and a plain cargo build does not.
---
 flake.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/flake.nix b/flake.nix
index 577caad6ca..937769bf1b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -170,6 +170,10 @@
 
           env = {
             CARGO_NET_GIT_FETCH_WITH_CLI = "true";
+            # nrf-mpsl-sys and nrf-sdc-sys run bindgen, which dlopens libclang
+            # at build-script time. Without this every nRF firmware build fails
+            # with "Unable to find libclang".
+            LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";
             RUST_MIN_STACK = "67108864";
             RUST_SRC_PATH = "${stableToolchain}/lib/rustlib/src/rust/library";
           };