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From: Sasha Levin <sashal@kernel.org>
To: sashiko-reviews@lists.linux.dev
Cc: Nathan Chancellor <nathan@kernel.org>,
	Nicolas Schier <nsc@kernel.org>,
	linux-kbuild@vger.kernel.org,
	Shuah Khan <shuah@kernel.org>,
	linux-kselftest@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Ian Rogers <irogers@google.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	James Clark <james.clark@linaro.org>,
	linux-perf-users@vger.kernel.org,
	=?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 2/7] kbuild: add "make tools_build" to build userspace tools from tools/
Date: Sun, 18 Oct 2026 10:39:42 -0400
Message-ID: <20261018143942.4113179-1-sashal@kernel.org>
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On Sat, Oct 17, 2026 at 02:32:09PM +0000, sashiko-bot@kernel.org wrote:
>> +dry-run := $(findstring n,$(firstword -$(MAKEFLAGS)))
>
>[Severity: Medium]
>Could this dry-run detection logic produce a false positive for common make
>arguments?
>
>If MAKEFLAGS starts with a long option containing 'n' (such as Kbuild's
>frequent default --no-print-directory), -$(MAKEFLAGS) evaluates to something
>like ---no-print-directory, and findstring erroneously matches the letter 'n'.
[...]
>Is it possible to use the standard Kbuild idiom here, like
>$(findstring n,$(filter-out --%,$(MAKEFLAGS))), to properly check the flags?

MAKEFLAGS does not start with a long option. With make 4.0 and later,
which the kernel requires, its first word holds the single letter
options and the long options follow after a space. With no single letter
options, -$(MAKEFLAGS) starts with "- --no-print-directory" and the
first word is "-". The top level Makefile detects -s the same way.

Under kbuild the first word is "-rR", as kbuild adds -rR to MAKEFLAGS. I
checked with make 4.4.1, calling Makefile.kbuild from a parent that adds
-rR --no-print-directory: dry-run is empty for a plain, -j, -k and -s
build, and is "n" only with -n.

-- 
Thanks,
Sasha