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Wed, 05 Mar 2025 09:40:58 +0100 Message-ID: Date: Wed, 5 Mar 2025 09:40:43 +0100 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: =?UTF-8?Q?Re=3A_=5BRFC=5D_Clarification_for_=E2=80=9Cundefined_beha?= =?UTF-8?B?dmlvdXLigJ0/?= To: Dan Carpenter , Dmitry Baryshkov , kernel-janitors@vger.kernel.org, freedreno@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org Cc: Abhinav Kumar , Archit Taneja , Daniel Vetter , David Airlie , Jeykumar Sankaran , Jordan Crouse , Marijn Suijten , Rob Clark , Sean Paul , Simona Vetter , Vinod Koul , cocci@inria.fr, LKML References: <40c60719-4bfe-b1a4-ead7-724b84637f55@web.de> <1a11455f-ab57-dce0-1677-6beb8492a257@web.de> <13566308-9a80-e4aa-f64e-978c02b1406d@web.de> <54c30a69-71cf-4582-9086-50eb0d39f273@web.de> <29b32b0d-312d-4848-9e26-9e5e76e527a7@stanley.mountain> Content-Language: en-GB From: Markus Elfring In-Reply-To: <29b32b0d-312d-4848-9e26-9e5e76e527a7@stanley.mountain> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:Is8r5OqTz1HEt5DAHK+q9bpWIsAC/ftPgUCj2FJLpX8MmfLUBid fT2UpE/JSWmezrvupm7xHOXC7YUQsVaEZC0V5+3kNBaub/aDJDNC2yqQbgrscneRvnBq5VX VMQxX2+7fAtLBuT/Uboe9GP66LH+LXdN/9wgjWAmtPLeF4ULKk2+AEV7mhfygbzhNi9V9wB tkXDOy8yRt6oKzQuoNYUA== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:MuuCeMBVWnM=;BzFg+FxRcOm4BpAgy0enxRtgIHL 4qupdcjxA6scJ3cX8W3kBIpdy/H4k+t7A4eNhegIC5Q6XRp9nWJQBpjEoqrBVWV3aH4tD043x N0gU9isZlYOwtTS2+LyVl4XTSrwTsx9DGUqM8FclDGpDUzwCX2k0jzWg5RyxTvsZnqJKQCe4u JVZTuYJciWMQninqJsMPiUKYGOP00FXKKXKNld2DOhORcvClqkBI2QfRW4VVhKwkZZwITIohN oczZRh0+LBz6HVJb6wvF/gdUDVSC6wA0UQSRVGmRuhEHP3tdilb/NDq38+A7X6ie/ca198CGY oAomEVGBLJox4XYcY4QknL7NBQ3MnFVBu1ZZBLq2A4jzTeym3S87sf+KERld9cMLN71ZaZDRt QqmBh1UbLqQmvai/mDJzSO26qqsemIOf6rxIlEuAJMzIoFjB8NR71+5N0PWrzjpQNE4hSb2uU Ez8c79sMcApnHnfe+9EBwBwq6fPsSd0fnYIUY189mQgmb4nRhFg/c604l9Wg03W1tABL2eimo rHlDCgJtEa2YT7asXccZOr5+Vh+lS719rBY9ATeYjD20CymYIqFDviVhNOmIPcVZrDAk9ycB0 fd9+3wj+9egR5Rm8TWep22kj2sqrk8t80TtPvP3SyoHITgIrrQFQDSPgTiiej2xcC6Uvn4ekS G5bib8BotNmdMcUBYyx0+iyiMTq/dYaOtHM5VycArSykz4QiKJLSe2QgSlaZA9ewnudX6ojvN ovWqLR3GQ5/ITBaschxQkJO5zAdWz7Ksv/9OORtm9iN83sgtdPEYyYrJpapIRS75p3/YONcb4 YM781c0t19a/FMrXy27nVhTRSItb3lp39Eq8S1Cr1Mc5YWYVK9lVKriOavWh0vfSGv+b5wrtp 4FxP4/kHn3bejmofRFRHDhydYsF++px1Z15ojeihiJbo5tsFqawhNk06ujULAPg7BewFds+bi TKEj4DZrPxdrkO3inYqmFm34uIw4RYfsvC3zUUW+jUsMQxSRSiBzuVp3wVM7Y6YbuPVghbTUw JpzrWYGYycUc2jKFuj4pcACdAeklii9U/6zuww4yAxDqYncKhWcLsNwA9omLPovtZVmKRhCsB PGkL9tts+aYt9K1JYYWIltzHeoLjzIt2cfs2F4KvQEKy4XhAW7oIASNELcIwklQP6MU+5IixI baJTU5mzorsYPb8a1ruASEdY3uOry7NjOUjLoBlgzkH2o8Tc+YG3U2cfn/UMSMdyrQXs+cucJ zUzG5qFlhXJbak8Fh/rJrfct5PDE62PaRceFlW/z8jAYf+nAZye5+yMTAq8kyg26/im3np92p oeQ9Xn6WleJZtWsVOphZEbFXw03x9jODGJXYF7633qYzfD+pOLMxUZrzYKMozCrd6V9zc/DgV IJ7dM6wYNVQXmq7yYsUr8HNhRjW3XZAvSIhs54WzvxvXbY4LTNW9at5SvzPYTfJcM1K2DRVXz SgLwmhV+mstgAnG2q0CJRo1aqMEI= >>> The address of a data structure member was determined before >>> a corresponding null pointer check in the implementation of >>> the functions =E2=80=9Cdpu_hw_pp_enable_te=E2=80=9D and =E2=80=9Cdpu_h= w_pp_get_vsync_info=E2=80=9D. >>> >>> Thus avoid the risk for undefined behaviour by removing extra >>> initialisations for the variable =E2=80=9Cc=E2=80=9D (also because it = was already >>> reassigned with the same value behind this pointer check). > There is no undefined behavior here. Is there a need to improve the wording precision? There are words which denote a special meaning according to aspects of the programming language =E2=80=9CC=E2=80=9D. https://en.cppreference.com/w/c/language/behavior Dereferences of null pointers are treated in special ways. The system might be configurable to collaborate also with data accesses together with the address =E2=80=9Czero=E2=80=9D. Would you like to distinguish supported software functionality any further= ? Regards, Markus