linux-kernel - Re: [PATCH 3/8] bpftool: Conditionally add -Wformat-signedness flag

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Message-ID: <52fe87ef-0797-4cf1-9e70-dc218f904e77@kernel.org>
Date: Thu, 25 Sep 2025 11:42:39 +0100
From: Quentin Monnet <qmo@...nel.org>
To: Leo Yan <leo.yan@....com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 Andrii Nakryiko <andrii@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 James Clark <james.clark@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 llvm@...ts.linux.dev, bpf@...r.kernel.org
Subject: Re: [PATCH 3/8] bpftool: Conditionally add -Wformat-signedness flag

2025-09-25 11:26 UTC+0100 ~ Leo Yan <leo.yan@....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@....com>


Hi, how annoying is this warning? 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.

Quentin


[0]
https://github.com/llvm/llvm-project/commit/ea92b1f9d0fc31f1fd97ad04eb0412003a37cb0d