[PATCH] run-clang-tools: Resolve the compilation database before changing directory

[PATCH] run-clang-tools: Resolve the compilation database before changing directory

[Marcus]

The script reads the compilation database relative to its working
directory, but passes the same path to clang-tidy after switching to each
entry's directory. When the database is outside the build directory, a
relative path can therefore point to a nonexistent location. clang-tidy
then runs without the recorded compilation flags or finds an unrelated
database in a parent directory.

For example, invoking the script with database/compile_commands.json from
the parent of database/ and build/ fails to load the database when its
entries use build/ as their directory.

After reading the JSON file, resolve its containing directory to an
absolute path for clang-tidy's -p option. This preserves the caller's path
resolution when the subprocess changes directory.

The issue, fix, and reproducer were developed with OpenAI Codex assistance.
Verified with Python 3.13 and clang-tidy 23.1.4 using a C file requiring a
definition from the database, with relative and absolute database paths
outside the build directory and a database in the working directory.

Fixes: 6ad7cbc01527 ("Makefile: Add clang-tidy and static analyzer support to makefile")
Signed-off-by: Marcus <baronmarcus2005@gmail.com>
---
 scripts/clang-tools/run-clang-tools.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/clang-tools/run-clang-tools.py b/scripts/clang-tools/run-clang-tools.py
index 79d58b34..cc19f8bb 100755
--- a/scripts/clang-tools/run-clang-tools.py
+++ b/scripts/clang-tools/run-clang-tools.py
@@ -86,6 +86,8 @@ def main():
     with open(args.path) as f:
         datastore = json.load(f)
 
+    args.path = os.path.dirname(os.path.abspath(args.path))
+
     lock = multiprocessing.Lock()
     try:
         with multiprocessing.Pool(initializer=init, initargs=(lock, args)) as pool:

base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb
-- 
2.51.2.windows.1

Re: [PATCH] run-clang-tools: Resolve the compilation database before changing directory

[Nathan Chancellor]

> The script reads the compilation database relative to its working
> directory, but passes the same path to clang-tidy after switching to each
> entry's directory. When the database is outside the build directory, a
> relative path can therefore point to a nonexistent location. clang-tidy
> then runs without the recorded compilation flags or finds an unrelated
> database in a parent directory.
> 
> For example, invoking the script with database/compile_commands.json from
> the parent of database/ and build/ fails to load the database when its
> entries use build/ as their directory.

I do not believe this script is meant to be called arbitrarily by a
user. It is only designed to be called within Kbuild directly via the
clang-tidy and clang-analyzer targets. The rules for those targets
mandate using the current build's compile_commands.json through their
prerequisites, so the script's current working directory must be the
same as the directory of every entry in compile_commands.json, so I do
not think your reproducer can happen in practice. If it can happen
through using one of those targets, please demonstrate how.

-- 
Cheers,
Nathan