linux-kernel - Re: [PATCH v2 0/8] perf build: Support building with Clang

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Message-ID: <20251001152217.GQ7985@e132581.arm.com>
Date: Wed, 1 Oct 2025 16:22:17 +0100
From: Leo Yan <leo.yan@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	James Clark <james.clark@...aro.org>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, llvm@...ts.linux.dev,
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 0/8] perf build: Support building with Clang

On Wed, Oct 01, 2025 at 11:21:20AM -0300, Arnaldo Carvalho de Melo wrote:
> On Tue, Sep 30, 2025 at 05:54:48PM +0100, Leo Yan wrote:
> > This series adds support for building perf with Clang, following the
> > discussion in [1]. Because the Android NDK uses Clang by default,
> > enabling Clang builds naturally covers Android as well.
> > 
> > The series is organized as follows:
> > 
> >   - Patches 1–2: Fix two bugs found with Clang.
> >   - Patches 3–6: Correct CROSS_ARCH and dismiss Clang build warnings.
> >   - Patches 7–8: Enable Clang in the Makefile and update the
> >     documentation.
> > 
> > Testing:
> > 
> >   - Clang 15.0.7 on Ubuntu 22.04.5: native and cross-compiling (aarch64)
> >   - Clang 18.1.3 on Ubuntu 24.04.2: native and cross-compiling (aarch64)
> >   - Android NDK r27d (latest LTS): cross-compiling (aarch64)
> 
>   LD      /tmp/build/perf/util/perf-util-in.o
>   LD      /tmp/build/perf/perf-util-in.o
>   AR      /tmp/build/perf/libperf-util.a
>   CC      /tmp/build/perf/pmu-events/pmu-events.o
>   LD      /tmp/build/perf/pmu-events/pmu-events-in.o
>   AR      /tmp/build/perf/libpmu-events.a
>   LINK    /tmp/build/perf/perf
> make: Leaving directory '/git/perf-6.17.0-rc6/tools/perf'
> + rm -rf /tmp/build/perf
> + mkdir /tmp/build/perf
> + make 'ARCH=' 'CROSS_COMPILE=' 'EXTRA_CFLAGS=' -C tools/perf 'O=/tmp/build/perf' 'CC=clang'
> make: Entering directory '/git/perf-6.17.0-rc6/tools/perf'
>   BUILD:   Doing 'make -j28' parallel build
> Makefile.config:494: *** No gnu/libc-version.h found, please install glibc-dev[el].  Stop.
> make[1]: *** [Makefile.perf:289: sub-make] Error 2
> make: *** [Makefile:76: all] Error 2
> make: Leaving directory '/git/perf-6.17.0-rc6/tools/perf'
> + exit 1
> toolsbuilder@...e:~$ cat dm.log/alpine\:3.22

A quick look: the build cannot find both libelf (feature-libelf=0) and
glibc (feature-glibc=0), thus lead to build failure. It is good to
know what the reason for the feature building failures:

  tools/perf/feature/test-libelf.make.output
  tools/perf/feature/test-glibc.make.output

I am not surprised for the failure of libelf (this is common case
that the package is not installed by default in a distro), but it is a
bit confused for the glibc feature failure.

It seems the issue occurs on Alpine 3.22, but the highest version
supported in container-build is 3.21 [1]. Could you confirm whether
the issue reproduces on other distros or versions?

Thanks,
Leo

[1] https://github.com/acmel/linux-tools-container-builds/tree/main/alpine