From 247f4425b9f11e5176be084b76f38ca7ca632870 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20M=C3=BChlbacher?= <tmuehlbacher@posteo.net>
Date: Tue, 15 Sep 2026 01:46:34 +0200
Subject: [PATCH 1/3] llvmPackages.clang-tools: ensure wrapper uses bash

The wrapper script relies on features only available with bash, namely
arithmetic evaluation as in `while (( $# )); do`. So let's ensure that
the shebang is patched to use bash. (bash's POSIX `sh` evaluates this as
intended.)

A minimal reproducer with a project that generally ought to pass
clang-tidy checking may look like so:

```nix
{
  pkgs ? import <nixpkgs> { },
}:
pkgs.fwupd.overrideAttrs (
  final: prev: {
    nativeBuildInputs = prev.nativeBuildInputs ++ [ pkgs.clang-tools ];
    preCheck = ''
      ninja clang-tidy
    '';
  }
)
```

Before, you may see many errors about missing headers and some lines
that suspiciously look like bash errors.

```
fwupd> >>> /nix/store/gf6qdh329rc8lbby710r9rzhwqkkgv3h-clang-tools-21.1.8/bin/clang-tidy --use-color -quiet -p /build/source/build /build/source/plugins/uf2/fu-self-test.c
fwupd> /nix/store/gf6qdh329rc8lbby710r9rzhwqkkgv3h-clang-tools-21.1.8/bin/clang-tidy: line 5: 129: not found
fwupd> /nix/store/gf6qdh329rc8lbby710r9rzhwqkkgv3h-clang-tools-21.1.8/bin/clang-tidy: line 23: 129: not found
fwupd> 276 warnings and 1 error generated.
fwupd> Error while processing /build/source/plugins/uf2/fu-self-test.c.
fwupd> /nix/store/dm7fg33sqnjxkwdpirnnbnx7wyi89m82-glib-2.88.3-dev/include/glib-2.0/glib/gtypes.h:41:10: error: 'time.h' file not found [clang-diagnostic-error]
fwupd>    41 | #include <time.h>
fwupd>       |          ^~~~~~~~
```

With this change, these clang-tidy errors no longer appear.
---
 pkgs/development/compilers/llvm/common/clang-tools/default.nix | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pkgs/development/compilers/llvm/common/clang-tools/default.nix b/pkgs/development/compilers/llvm/common/clang-tools/default.nix
index 91daa95d07cf..74523db10b80 100644
--- a/pkgs/development/compilers/llvm/common/clang-tools/default.nix
+++ b/pkgs/development/compilers/llvm/common/clang-tools/default.nix
@@ -3,6 +3,7 @@
   stdenv,
   runCommand,
   writeText,
+  bashNonInteractive,
   clang-unwrapped,
   clang,
   libcxxClang,
@@ -20,6 +21,8 @@ stdenv.mkDerivation (finalAttrs: {
   strictDeps = true;
   __structuredAttrs = true;
 
+  buildInputs = [ bashNonInteractive ];
+
   installPhase = ''
     runHook preInstall
 

From c37c7bbcdb0d1bb51bc497f85194f97be2bf859b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20M=C3=BChlbacher?= <tmuehlbacher@posteo.net>
Date: Thu, 17 Sep 2026 00:52:48 +0200
Subject: [PATCH 2/3] llvmPackages.clang-tools: use correct shell shebang

This wrapper is factually a bash script and should therefore use the
correct shebang instead of relying on the leniency of the bash POSIX
mode.
---
 pkgs/development/compilers/llvm/common/clang-tools/wrapper | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/development/compilers/llvm/common/clang-tools/wrapper b/pkgs/development/compilers/llvm/common/clang-tools/wrapper
index 6601d6875f8e..247d858b9488 100755
--- a/pkgs/development/compilers/llvm/common/clang-tools/wrapper
+++ b/pkgs/development/compilers/llvm/common/clang-tools/wrapper
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 buildcpath() {
   local path after

From 5bf21ff317f377d7dd3e417e3b583d15852a3a4d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20M=C3=BChlbacher?= <tmuehlbacher@posteo.net>
Date: Thu, 17 Sep 2026 00:55:02 +0200
Subject: [PATCH 3/3] llvmPackages.clang-tools: add test for clang-tidy

While the wrapper's bash script was broken, clang-tidy would have failed
to check a project with an include such as assert.h because it wouldn't
have been able to find that header file.
---
 .../compilers/llvm/common/clang-tools/default.nix           | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pkgs/development/compilers/llvm/common/clang-tools/default.nix b/pkgs/development/compilers/llvm/common/clang-tools/default.nix
index 74523db10b80..4fab7f98164d 100644
--- a/pkgs/development/compilers/llvm/common/clang-tools/default.nix
+++ b/pkgs/development/compilers/llvm/common/clang-tools/default.nix
@@ -66,9 +66,11 @@ stdenv.mkDerivation (finalAttrs: {
   passthru.tests =
     let
       src = writeText "main.cpp" ''
+        #include <assert.h>
         #include <iostream>
 
         int main() {
+          assert(true);
           std::cout << "Hi!";
         }
       '';
@@ -79,6 +81,10 @@ stdenv.mkDerivation (finalAttrs: {
         ${finalAttrs.finalPackage}/bin/clangd  --check=${src}
         touch $out
       '';
+      smokeOkClangTidy = runCommand "clang-tidy-test-smoke-ok" { } ''
+        ${finalAttrs.finalPackage}/bin/clang-tidy ${src}
+        touch $out
+      '';
       smokeErr = runCommand "clang-tools-test-smoke-err" { } ''
         (${finalAttrs.finalPackage}/bin/clangd --query-driver='**' --check=${src} 2>&1 || true) \
             | grep 'use of undeclared identifier'