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(2a02-8389-41cf-e200-91b0-e3db-0523-0d17.cable.dynamic.v6.surfer.at. [2a02:8389:41cf:e200:91b0:e3db:523:d17]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37cd56e6587sm10154402f8f.47.2024.09.30.13.46.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Sep 2024 13:46:05 -0700 (PDT) Message-ID: Date: Mon, 30 Sep 2024 22:46:04 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: linux-6.12-rc1/drivers/iio/imu/bmi323/bmi323_core.c:133: Array contents defined but not used ? To: Nathan Chancellor Cc: David Binderman , "jagathjog1996@gmail.com" , "jic23@kernel.org" , "lars@metafoo.de" , "linux-iio@vger.kernel.org" , Linux Kernel Mailing List References: <7e9ae281-448c-429b-9ca5-86581f777f68@gmail.com> <20240930151542.GA3556370@thelio-3990X> <0342111e-47f7-4981-a1f1-e694392fa741@gmail.com> <20240930202642.GA1497385@thelio-3990X> Content-Language: en-US, de-AT From: Javier Carrasco In-Reply-To: <20240930202642.GA1497385@thelio-3990X> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 30/09/2024 22:26, Nathan Chancellor wrote: > Hi Javier, > > On Mon, Sep 30, 2024 at 06:50:14PM +0200, Javier Carrasco wrote: >> But if that wasn't the case, and since you can't use sizeof(), >> should it be marked with __maybe_unused / __attribute__((unused)) even >> though it's known in advance that it won't be used, or at least that its >> use will be to get its size? > > Correct. > >> Is it then just to silence the warning, or does it have other >> implications? Thanks again! > > Yes, the use of the unused attribute would just be to silence the > warning; the variable would still not be emitted in the final binary. > clang's behavior matches GCC's (aside from the special warning): > > https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute > > If the variable needed to be emitted in the object file, > __attribute__((used)) would need to be used, which explicitly has code > generation implications: > > https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute > > A contrived example: > > https://godbolt.org/z/oGGbqK98o > > Cheers, > Nathan Thanks a lot for spoon-feeding it to me :) Best regards, Javier Carrasco