Re: [RFC PATCH] kbuild: Add option to generate a Compilation Database

[Tom Roeder <tmroeder@google.com>]

On Thu, Jun 06, 2019 at 04:40:00PM -0700, Nick Desaulniers wrote:
> On Thu, Jun 6, 2019 at 1:54 PM Tom Roeder <tmroeder@google.com> wrote:
> >
> > On Thu, Jun 06, 2019 at 02:30:03PM -0600, Raul E Rangel wrote:
> > > Clang tooling requires a compilation database to figure out the build
> > > options for each file. This enables tools like clang-tidy and
> > > clang-check.
> > >
> > > See https://clang.llvm.org/docs/HowToSetupToolingForLLVM.html for more
> > > information.
> 
> I'm also super happy to see this!
> https://nickdesaulniers.github.io/blog/2017/05/31/running-clang-tidy-on-the-linux-kernel/
> I don't know enough about GNU Make/Kbuild to answer the questions, but
> hopefully Masahiro can help there.
> 
> > I'm glad to see someone adding this to the Makefile directly. I added
> > scripts/gen_compile_commands.py in b302046 (in Dec 2018) when I was
> 
> Heh, cool.  I had a script that basically did this; we recently
> dropped it from the Android trees when doing an audit of out of tree
> patches.
> 
> > working on using clang-check to look for bugs in KVM. That script
> 
> I'm very interested in this work; my summer intern is looking into
> static analyses of the Linux kernel.  Can you maybe reach out to me
> off thread to tell me more about what you found (or didn't)?
> 
> > > Normally cmake is used to generate the compilation database, but the
> > > linux kernel uses make. Another option is using
> > > [BEAR](https://github.com/rizsotto/Bear) which instruments
> > > exec to find clang invocations and generate the database that way.
> 
> It's probably possible to get this to work w/ GCC if the additional
> dependency of bear exists on the host's system (and may reduce the
> number of implementations).  Downside is the additional host
> dependency.
> 
> Sounds like it may also be possible to just run
> scripts/gen_compile_commands.py at build time if this config is
> enabled?

Yes, for scripts/gen_compile_commands.py, you run a build first with
whatever configuration you want, then call the script to produce the
compile_commands.json file.