From: Leo Yan <leo.yan@arm.com>
To: Quentin Monnet <qmo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Andrii Nakryiko <andrii@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
James Clark <james.clark@linaro.org>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
llvm@lists.linux.dev, bpf@vger.kernel.org
Subject: Re: [PATCH 3/8] bpftool: Conditionally add -Wformat-signedness flag
Date: Thu, 25 Sep 2025 13:43:16 +0100 [thread overview]
Message-ID: <20250925124316.GA7985@e132581.arm.com> (raw)
In-Reply-To: <52fe87ef-0797-4cf1-9e70-dc218f904e77@kernel.org>
On Thu, Sep 25, 2025 at 11:42:39AM +0100, Quentin Monnet wrote:
> 2025-09-25 11:26 UTC+0100 ~ Leo Yan <leo.yan@arm.com>
> > clang-18.1.3 on Ubuntu 24.04.2 reports warning:
> >
> > warning: unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]
> >
> > Conditionally add the option only when it is supported by compiler.
> >
> > Signed-off-by: Leo Yan <leo.yan@arm.com>
>
>
> Hi, how annoying is this warning?
Not too bad, it prints out 5~6 times warnings (see the build log below).
Though the warnings are a bit noisy, they does not break the build.
> I'm asking because as far as I
> understand, the option has been introduced in LLVM 19.1.0 [0] - the
> latest being 21.1.0 already - so we won't need this check once distros
> have transitioned, and I'm a bit reluctant to add it.
I agree the warning likely won't affect distros, as package maintainers
will hide it. But it can annoy _paranoid_ developers in day-to-day
builds ;)
As the warning doesn't block anything, so I am fine with not merging
this patch.
Thanks,
Leo
> [0]
> https://github.com/llvm/llvm-project/commit/ea92b1f9d0fc31f1fd97ad04eb0412003a37cb0d
---8<---
Auto-detecting system features:
... clang-bpf-co-re: [ on ]
... llvm: [ OFF ]
... libcap: [ on ]
... libbfd: [ OFF ]
... libbfd-liberty: [ OFF ]
... libbfd-liberty-z: [ OFF ]
... disassembler-four-args: [ OFF ]
... disassembler-init-styled: [ OFF ]
... libelf-zstd: [ o
MKDIR /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf
MKDIR /build/util/bpf_skel/.tmp/bootstrap/libbpf/
MKDIR /build/util/bpf_skel/.tmp/bootstrap/
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/hashmap.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/relo_core.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/libbpf_internal.h
warning: unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]
1 warning generated.
GEN /build/util/bpf_skel/.tmp/bootstrap/libbpf/bpf_helper_defs.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/bpf.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/libbpf.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/libbpf_legacy.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/btf.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/bpf_helpers.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/libbpf_common.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/bpf_tracing.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/bpf_core_read.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/bpf_endian.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/libbpf_version.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/skel_internal.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/usdt.bpf.h
INSTALL /build/util/bpf_skel/.tmp/bootstrap/libbpf/include/bpf/bpf_helper_defs.h
INSTALL libbpf_headers
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/libbpf.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/bpf.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/nlattr.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/btf.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/libbpf_errno.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/str_error.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/netlink.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/bpf_prog_linfo.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/libbpf_probes.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/hashmap.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/btf_dump.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/ringbuf.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/strset.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/gen_loader.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/relo_core.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/linker.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/usdt.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/zip.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/elf.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/features.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/btf_iter.o
CC /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/btf_relocate.o
LD /build/util/bpf_skel/.tmp/bootstrap/libbpf/staticobjs/libbpf-in.o
LINK /build/util/bpf_skel/.tmp/bootstrap/libbpf/libbpf.a
CC /build/util/bpf_skel/.tmp/bootstrap/main.o
CC /build/util/bpf_skel/.tmp/bootstrap/common.o
CC /build/util/bpf_skel/.tmp/bootstrap/json_writer.o
CC /build/util/bpf_skel/.tmp/bootstrap/gen.o
CC /build/util/bpf_skel/.tmp/bootstrap/btf.o
warning: unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]
warning: unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]
warning: unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]warning:
unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]
warning: unknown warning option '-Wformat-signedness' [-Wunknown-warning-option]
1 warning generated.
1 warning generated.
1 warning generated.
1 warning generated.
1 warning generated.
LINK /build/util/bpf_skel/.tmp/bootstrap/bpftool
next prev parent reply other threads:[~2025-09-25 12:43 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-25 10:26 [PATCH 0/8] perf build: Support building with Clang Leo Yan
2025-09-25 10:26 ` [PATCH 1/8] tools build: Align warning options with perf Leo Yan
2025-09-25 10:26 ` [PATCH 2/8] perf python: split Clang options when invoking Popen Leo Yan
2025-09-25 10:26 ` [PATCH 3/8] bpftool: Conditionally add -Wformat-signedness flag Leo Yan
2025-09-25 10:42 ` Quentin Monnet
2025-09-25 12:43 ` Leo Yan [this message]
2025-09-25 10:26 ` [PATCH 4/8] perf test coresight: Dismiss clang warning for memcpy thread Leo Yan
2025-09-25 19:38 ` Ian Rogers
2025-09-26 16:19 ` Leo Yan
2025-09-25 10:26 ` [PATCH 5/8] perf test coresight: Dismiss clang warning for thread loop Leo Yan
2025-09-25 10:26 ` [PATCH 6/8] perf test coresight: Dismiss clang warning for unroll loop thread Leo Yan
2025-09-25 10:26 ` [PATCH 7/8] perf build: Support build with clang Leo Yan
2025-09-25 10:26 ` [PATCH 8/8] perf docs: Document building with Clang Leo Yan
2025-09-25 19:43 ` Ian Rogers
2025-09-26 15:41 ` Leo Yan
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