json-compilation-database: Error while opening JSON database: Not a directory

[max-kamps]

When I pass a compilation database to c2rust (running LLVM 22.1.5 on Linux), the following message is repeated for every input file:

Error while trying to load a compilation database:
Could not auto-detect compilation database from directory "/projectdir/compile_commands.json"
No compilation database found in /projectdir/compile_commands.json or any parent directory
json-compilation-database: Error while opening JSON database: Not a directory
fixed-compilation-database: Error while opening fixed database: Not a directory
Running without flags.

And indeed, none of the flags in the compilation database are used, causing errors.

Debugging a bit, it seems the way c2rust passes the build file to libtooling (-p <path-to-json-file>) is incorrect, at least for LLVM 22. It expects the build path passed in with -p to be a directory containing compile_commands.json.

CompilationDatabase::autoDetectFromDirectory seems to be the relevant function here.

[ahomescu]

Are you running this from a directory that is a symlink? (either it or any of its ancestors) Try cd $(readlink -f .) and rerun the transpiler.

[max-kamps]

Nope, not in a symlink.

For what it's worth, changing this line:

c2rust/c2rust-ast-exporter/src/lib.rs

Line 66 in 5594ab8

args_owned.push(CString::new(cc_db.to_str().unwrap()).unwrap());

to passing the parent directory instead of the json file, like this:

args_owned.push(CString::new(cc_db.parent().unwrap().to_str().unwrap()).unwrap());`

fixed the issue for me.

Not sure if this is the correct solution or if this breaks something else.