linux-kernel - Re: clangd cannot handle tree

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Message-ID: <CAKwvOdnxCJo-FoPfcNw=SBum6yRXOY7_meT8T6gsjV3c3FFm5A@mail.gmail.com>
Date:   Tue, 18 Apr 2023 13:46:40 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     rcu@...r.kernel.org, nathan@...nel.org, trix@...hat.com,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        paulmck@...nel.org
Subject: Re: clangd cannot handle tree_nocb.h

On Tue, Apr 18, 2023 at 1:36 PM Joel Fernandes <joel@...lfernandes.org> wrote:
>
> On Fri, Apr 14, 2023 at 03:47:51PM -0700, Nick Desaulniers wrote:
> > On Thu, Apr 13, 2023 at 5:53 PM Joel Fernandes <joel@...lfernandes.org> wrote:
> > >
> > > Hello!
> > >
> > > I have been trying to get clangd working properly with tree_nocb.h. clangd
> > > trips quite badly when trying to build tree_nocb.h to generate ASTs.
> >
> > Hi Joel,
> > Thanks for the report.  What are you using clangd for? I'll bet
> > something interesting.
>
> Thanks for the response and sorry for the late reply. I am at the OSPM
> conference. I use vim and vscode with clangd. In vim, YCM uses it to
> highlight compiler errors live while editing, I am pretty happy with it so
> far and has been a huge time saver. Enough that now I want to use it for
> everything...

Cool! I use vim, can you share more info about your set up for this?
I'll have to try it.

>
> I first came across clangd when developing Chrome userspace code which is C++
> :). In Chrome, ninja builds can be made to output compile_commands.json.
> However, now I noticed the support in the kernel and was like, wow I need to
> try it. Further, YCM seems to work much better with it than without :)
>
> > I've never used it myself, so I don't know where to even begin with
> > how to reproduce the issue.
>
> Ah ok. :). When I ran get_maintainer on the script, your name popped up and
> someone also suggested that you're the goto person for clang on the kernel
> (which I kind of already knew ;)

You've cc'ed the right set of folks.  We might not have the expertise
related to clangd specifically, but we can point you in the right
direction.

>
> > It might be worth filing a bug upstream at
> > https://github.com/llvm/llvm-project/issues
> > or internally under the component
> > Language Platforms > C++ > Clang > Tools > Clangd
> > with detailed steps to reproduce (and what the observed error actually
> > is). Feel free to cc me, though I don't know the first thing about
> > clangd.
>
> Ok I will consider doing this if needed. One thing I do observe is lack of
> good support for header files and it is a known clangd issue [1].
>
> However, the fixes I was proposing can purely be done in the kernel itself
> since all it'd require is generating compile_compands.json with the -D<macro>
> and editing files to keep clangd happy. I guess one question is, how welcome
> would such changes to header files be since they're for tooling and isn't
> code that will be compiled outside of clangd.

Specifically your patch sites some log print that doesn't look
indicative of a failure:
https://github.com/llvm/llvm-project/blob/53430bfd5c9d0074dd6de06dccea366e1d40bce4/clang-tools-extra/clangd/TUScheduler.cpp#L903-L906
so something else is going on here. Just trying to make sure we root cause this.

>
> (Linked issue may not directly related to what I'm saying)
> [1] https://discourse.llvm.org/t/header-file-heuristics-issue/1749
>
> Thanks.
>


-- 
Thanks,
~Nick Desaulniers