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SubjectRe: [PATCH] scripts: add a tool to produce a compile_commands.json file
On Fri, Dec 7, 2018 at 7:24 AM Tom Roeder <> wrote:
> The LLVM/Clang project provides many tools for analyzing C source code.
> Many of these tools are based on LibTooling
> (, 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/, 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, 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 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
> make
> scripts/
> 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
> line.
> 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: Tom Roeder <>

I am fine with this,
but I have one question.

The generated compile_commands.json
contains $(pound)

How is it handled?
Should it be replaced with '\#' ?

Best Regards
Masahiro Yamada

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