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

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Message-ID: <aN1yNKxXLnMtQczW@x1>
Date: Wed, 1 Oct 2025 15:25:56 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Leo Yan <leo.yan@....com>
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 04:22:17PM +0100, Leo Yan wrote:
> 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?

It was in all alpine versions I have containers to test on:

toolsbuilder@...e:~$ grep FAIL dm.log.old/summary 
   3    71.85 almalinux:9-i386              : FAIL clang version 17.0.6 (AlmaLinux OS Foundation 17.0.6-5.el9)
   5    78.60 alpine:3.16                   : FAIL gcc version 11.2.1 20220219 (Alpine 11.2.1_git20220219) 
   6    59.77 alpine:3.17                   : FAIL gcc version 12.2.1 20220924 (Alpine 12.2.1_git20220924-r4) 
   7    56.89 alpine:3.18                   : FAIL gcc version 12.2.1 20220924 (Alpine 12.2.1_git20220924-r10) 
   8    60.86 alpine:3.19                   : FAIL gcc version 13.2.1 20231014 (Alpine 13.2.1_git20231014) 
   9    60.18 alpine:3.20                   : FAIL gcc version 13.2.1 20240309 (Alpine 13.2.1_git20240309) 
  10    64.58 alpine:3.22                   : FAIL gcc version 14.2.0 (Alpine 14.2.0) 
  11    63.36 alpine:edge                   : FAIL gcc version 14.2.0 (Alpine 14.2.0) 
toolsbuilder@...e:~$

  GEN     /tmp/build/perf/python/perf.cpython-312-x86_64-linux-musl.so
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:~
$

lemme try to reapply those patches and get the
tools/perf/feature/test-libelf.make.output and
tools/perf/feature/test-glibc.make.output files.

- Arnaldo