linux-kernel - Re: [GIT PULL] kbuild changes for v6.19

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Message-ID: <20251217083202.GA2118121@ax162>
Date: Wed, 17 Dec 2025 17:32:02 +0900
From: Nathan Chancellor <nathan@...nel.org>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Nicolas Schier <nsc@...nel.org>, patso@...ewhatevs.io,
	Justin Stitt <justinstitt@...gle.com>, eddyz87@...il.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	regressions@...ts.linux.dev
Subject: Re: [GIT PULL] kbuild changes for v6.19

On Wed, Dec 17, 2025 at 05:16:02PM +0900, Dmitry Vyukov wrote:
> On Mon, 1 Dec 2025 at 16:38, Nicolas Schier <nsc@...nel.org> wrote:
> > Pat Somaru (1):
> >       scripts/clang-tools: Handle included .c files in gen_compile_commands
> 
> /\/\/\/\/\/\/\
> 
> This commit breaks invocation of clang tools for me.
> 
> For example I now have this fake entry for mock_uncore.c which
> pretends to produce intel_uncore.o (along with 2 other commands which
> produce the same object file):
...
> An attempt to invoke a clang tool using this database legitimately
> fails with the following errors (the file is not supposed and can't
> compile on its own):
> 
> clang-tool: drivers/gpu/drm/i915/selftests/mock_uncore.c: exit status 1
> drivers/gpu/drm/i915/selftests/mock_uncore.c:47:2: error: call to
> undeclared function 'ASSIGN_RAW_WRITE_MMIO_VFUNCS'; ISO C99 and later
> do not support implicit function declarations
> [-Wimplicit-function-declaration]
>    47 |         ASSIGN_RAW_WRITE_MMIO_VFUNCS(uncore, nop);
>       |         ^
> drivers/gpu/drm/i915/selftests/mock_uncore.c:47:39: error: use of
> undeclared identifier 'nop'; did you mean 'nopv'?
>    47 |         ASSIGN_RAW_WRITE_MMIO_VFUNCS(uncore, nop);
>       |                                              ^~~
>       |                                              nopv
> /arch/x86/include/asm/hypervisor.h:71:13: note: 'nopv' declared here
>    71 | extern bool nopv;
>       |             ^
> drivers/gpu/drm/i915/selftests/mock_uncore.c:48:2: error: call to
> undeclared function 'ASSIGN_RAW_READ_MMIO_VFUNCS'; ISO C99 and later
> do not support implicit function declarations
> [-Wimplicit-function-declaration]
>    48 |         ASSIGN_RAW_READ_MMIO_VFUNCS(uncore, nop);
>       |         ^
> drivers/gpu/drm/i915/selftests/mock_uncore.c:48:38: error: use of
> undeclared identifier 'nop'; did you mean 'nopv'?
>    48 |         ASSIGN_RAW_READ_MMIO_VFUNCS(uncore, nop);
>       |                                             ^~~
>       |                                             nopv
> /arch/x86/include/asm/hypervisor.h:71:13: note: 'nopv' declared here
>    71 | extern bool nopv;
>       |             ^
> 4 errors generated.
> Error while processing /drivers/gpu/drm/i915/selftests/mock_uncore.c.
> 
> 
> What am I doing wrong?

Nothing. As you note, ASSIGN_RAW_WRITE_MMIO_VFUNCS is defined in
drivers/gpu/drm/i915/intel_uncore.c but it is used in
drivers/gpu/drm/i915/selftests/mock_uncore.c, which is not designed to
be built standalone. We could potentially move
ASSIGN_RAW_WRITE_MMIO_VFUNCS into a common header to avoid this but I
think I would rather just revert 9362d34acf91, as I already figured that
this was going to be fragile:

  https://lore.kernel.org/20251007163338.GA547361@ax162/

I would rather discourage including .c files if folks want clangd to
work properly since this seems fundamentally unsolvable if developers
have written .c files in this manner. I am open to other thoughts
though.

Cheers,
Nathan