• Tom Roeder's avatar
    scripts: add a tool to produce a compile_commands.json file · b3020464
    Tom Roeder authored
    The LLVM/Clang project provides many tools for analyzing C source code.
    Many of these tools are based on LibTooling
    (https://clang.llvm.org/docs/LibTooling.html), which depends on a
    database of compiler flags. The standard container for this database is
    compile_commands.json, which consists of a list of JSON objects, each
    with "directory", "file", and "command" fields.
    Some build systems, like cmake or bazel, produce this compilation
    information directly. Naturally, Makefiles don't. However, the kernel
    makefiles already create .<target>.o.cmd files that contain all the
    information needed to build a compile_commands.json file.
    So, this commit adds scripts/gen_compile_commands.py, which recursively
    searches through a directory for .<target>.o.cmd files and extracts
    appropriate compile commands from them. It writes a
    compile_commands.json file that LibTooling-based tools can use.
    By default, gen_compile_commands.py starts its search in its working
    directory and (over)writes compile_commands.json in the working
    directory. However, it also supports --output and --directory flags for
    out-of-tree use.
    Note that while gen_compile_commands.py enables the use of clang-based
    tools, it does not require the kernel to be compiled with clang. E.g.,
    the following sequence of commands produces a compile_commands.json file
    that works correctly with LibTooling.
    make defconfig
    Also note that this script is written to work correctly in both Python 2
    and Python 3, so it does not specify the Python version in its first
    For an example of the utility of this script: after running
    gen_compile_commands.json on the latest kernel version, I was able to
    use Vim + the YouCompleteMe pluging + clangd to automatically jump to
    definitions and declarations. Obviously, cscope and ctags provide some
    of this functionality; the advantage of supporting LibTooling is that it
    opens the door to many other clang-based tools that understand the code
    directly and do not rely on regular expressions and heuristics.
    Tested: Built several recent kernel versions and ran the script against
    them, testing tools like clangd (for editor/LSP support) and clang-check
    (for static analysis). Also extracted some test .cmd files from a kernel
    build and wrote a test script to check that the script behaved correctly
    with all permutations of the --output and --directory flags.
    Signed-off-by: default avatarTom Roeder <tmroeder@google.com>
    Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
gen_compile_commands.py 5.56 KB