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From: Markus Elfring <Markus.Elfring@web.de>
To: Dan Carpenter <dan.carpenter@linaro.org>,
	Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	kernel-janitors@vger.kernel.org, freedreno@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>,
	Archit Taneja <architt@codeaurora.org>,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@gmail.com>,
	Jeykumar Sankaran <jsanka@codeaurora.org>,
	Jordan Crouse <jordan@cosmicpenguin.net>,
	Marijn Suijten <marijn.suijten@somainline.org>,
	Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
	Simona Vetter <simona@ffwll.ch>, Vinod Koul <vkoul@kernel.org>,
	cocci@inria.fr, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] Clarification for “undefined behaviour”?
Date: Wed, 5 Mar 2025 09:40:43 +0100	[thread overview]
Message-ID: <e665514b-5a62-4afb-b267-7c320e4872af@web.de> (raw)
In-Reply-To: <29b32b0d-312d-4848-9e26-9e5e76e527a7@stanley.mountain>

>>> The address of a data structure member was determined before
>>> a corresponding null pointer check in the implementation of
>>> the functions “dpu_hw_pp_enable_te” and “dpu_hw_pp_get_vsync_info”.
>>>
>>> Thus avoid the risk for undefined behaviour by removing extra
>>> initialisations for the variable “c” (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 “C”.
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 “zero”.
Would you like to distinguish supported software functionality any further?

Regards,
Markus

  parent reply	other threads:[~2025-03-05  8:41 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <40c60719-4bfe-b1a4-ead7-724b84637f55@web.de>
     [not found] ` <1a11455f-ab57-dce0-1677-6beb8492a257@web.de>
     [not found]   ` <54a21fea-64e3-de67-82ef-d61b90ffad05@web.de>
2023-04-13 15:49     ` [PATCH] perf map: Delete two variable initialisations before null pointer checks in sort__sym_from_cmp() Ian Rogers
     [not found]   ` <d8ed4e5d-49d4-ca7e-1283-1ec166bf643d@web.de>
2023-04-14 17:13     ` [PATCH] media: atomisp: Move a variable assignment behind a null pointer check in atomisp_cp_general_isp_parameters() Andy Shevchenko
2023-04-16 13:12       ` Hans de Goede
     [not found]   ` <d2403b7a-c6cd-4ee9-2a35-86ea57554eec@web.de>
2023-04-14 15:22     ` [PATCH] nvdimm: Replace the usage of a variable by a direct function call in nd_pfn_validate() Alison Schofield
     [not found]       ` <88f4dd20-4159-2b66-3adc-9a5a68f9eec7@web.de>
2023-04-14 19:14         ` Alison Schofield
2023-04-14 17:15     ` Andy Shevchenko
     [not found]   ` <b98dcc94-13f3-a6cb-f5bd-f1f8644d87d1@web.de>
2023-04-17  7:44     ` [PATCH] media: mediatek: vcodec: Move a variable assignment behind condition checks in vdec_vp9_slice_single_decode() AngeloGioacchino Del Regno
2023-04-17  8:01     ` Hans Verkuil
     [not found]   ` <622ed461-059b-455f-8a7b-7200a834bdc4@web.de>
2023-04-17  7:58     ` [PATCH] media: au0828: Move a variable assignment behind condition checks in au0828_isoc_copy() Hans Verkuil
     [not found]   ` <2a746461-844a-2ad6-7b52-03f13fe1b9bf@web.de>
2023-04-17 16:25     ` [PATCH 0/9] GPU-DRM-nouveau: Adjustments for seven function implementations Karol Herbst
     [not found]   ` <5800e1f5-8681-e140-fef0-8b2c3b4b6efa@web.de>
2023-04-18 12:51     ` [PATCH] gfs2: Move a variable assignment behind a null pointer check in inode_go_dump() Andreas Gruenbacher
2026-07-13 12:04       ` Markus Elfring
     [not found]   ` <c18331ca-3de9-d433-f477-b04103958b9c@web.de>
2023-04-19 19:03     ` [PATCH] ASoC: SOF: Intel: hda-stream: Move three variable assignments behind condition checks in hda_dsp_iccmax_stream_hw_params() Pierre-Louis Bossart
     [not found]   ` <93913f0c-4699-cf9a-0f10-8edd478fd2b3@web.de>
2023-04-21  5:32     ` [PATCH 0/4] staging: rtl8712: Adjustments for process_link_qual() Philipp Hortmann
     [not found]   ` <14636275-4d26-d639-5f6e-293fc6d1c4c6@web.de>
2023-04-25 13:30     ` [PATCH] drm/bridge: it6505: Move a variable assignment behind a null pointer check in receive_timing_debugfs_show() Robert Foss
     [not found]       ` <6f758653-36c9-91a2-7bbc-278ae3f8ccee@web.de>
2023-04-27 15:10         ` Robert Foss
     [not found]           ` <14083012-2f19-3760-a840-d685fcedc15e@web.de>
2023-04-28 11:49             ` Robert Foss
     [not found]               ` <fa69384f-1485-142b-c4ee-3df54ac68a89@web.de>
2023-04-28 17:27                 ` [PATCH resent] " Robert Foss
     [not found]   ` <2258ce64-2a14-6778-8319-b342b06a1f33@web.de>
     [not found]     ` <89048a5f-2dbb-012c-41f5-7c300e8415f5@web.de>
2023-04-11 15:04       ` [PATCH 2/5] drm/amd/display: Move three variable assignments behind condition checks in trigger_hotplug() Christian König
2024-01-05 19:21     ` [PATCH 0/5] drm/amd: Adjustments for three function implementations Markus Elfring
     [not found]     ` <0d4b92ab-f7c2-4f18-f3c3-c0f82ba47fc8@web.de>
2023-04-11 13:59       ` [PATCH 1/5] drm/amdgpu: Move a variable assignment behind a null pointer check in amdgpu_ras_interrupt_dispatch() Felix Kuehling
2024-09-09  9:42       ` Markus Elfring
     [not found]   ` <f7967bee-f3f1-54c4-7352-40c39dd7fead@web.de>
2025-03-02 16:55     ` [PATCH RESEND] qed: Move a variable assignment behind a null pointer check in two functions Markus Elfring
2025-03-03  6:21       ` Michal Swiatkowski
2025-03-03  7:40         ` Dan Carpenter
2025-03-03  8:22           ` [RESEND] " Markus Elfring
2025-03-03  8:28             ` Dan Carpenter
2025-03-03 10:25               ` Markus Elfring
2025-03-03 17:35               ` [RESEND] " Kory Maincent
2025-03-03 17:55                 ` Markus Elfring
     [not found]   ` <86551e6f-d529-1ff6-6ce6-b9669d10e6cb@web.de>
2025-03-02 18:02     ` [PATCH RESEND] video: au1100fb: Move a variable assignment behind a null pointer check in au1100fb_setmode() Markus Elfring
2025-03-03  9:19       ` Uwe Kleine-König
2025-03-03 10:08         ` Dan Carpenter
2025-03-03 10:08           ` Dan Carpenter
2025-03-03 10:14           ` Dan Carpenter
2025-03-03 10:30           ` Uwe Kleine-König
2025-03-03 10:36             ` Markus Elfring
2025-03-03 10:53             ` [PATCH RESEND] " Dan Carpenter
2025-03-05 12:14               ` Markus Elfring
2025-03-05 17:07                 ` Helge Deller
2025-03-05 17:28                   ` Markus Elfring
2025-03-08 21:26         ` [PATCH RESEND] " Helge Deller
     [not found]   ` <10e10996-d53d-0733-6d90-a04f251812ba@web.de>
2023-04-21  5:09     ` [PATCH] usb: dwc2: gadget: Move a variable assignment behind condition checks in dwc2_hsotg_handle_outdone() Minas Harutyunyan
2025-03-02 20:00     ` [PATCH RESEND] " Markus Elfring
     [not found]   ` <624fb730-d9de-ba92-1641-f21260b65283@web.de>
2025-03-02 20:30     ` [PATCH RESEND] tipc: Reduce scope for the variable “fdefq” in tipc_link_tnl_prepare() Markus Elfring
2025-03-05  2:50       ` Jakub Kicinski
     [not found]   ` <13566308-9a80-e4aa-f64e-978c02b1406d@web.de>
2023-04-11 16:43     ` [PATCH] drm/msm/dpu: Delete a variable initialisation before a null pointer check in two functions Dmitry Baryshkov
2023-04-11 16:44     ` Abhinav Kumar
2025-03-02 20:56     ` [PATCH RESEND] " Markus Elfring
2025-03-02 23:01       ` Dmitry Baryshkov
2025-03-03  7:14         ` Dan Carpenter
2025-03-03  8:15           ` [RESEND] " Markus Elfring
2025-03-03  8:24             ` Dan Carpenter
2025-03-05  8:40           ` Markus Elfring [this message]
2025-03-05  8:51             ` [RFC] Clarification for “undefined behaviour”? Dan Carpenter
2025-03-05  9:20               ` Markus Elfring
2025-03-05 14:17               ` David Laight
2025-03-05 14:30                 ` Dan Carpenter
2025-03-05 21:35                   ` David Laight
     [not found]   ` <fffd36dd-ec5d-4678-9e63-c52b0a711e76@web.de>
2025-03-03  9:11     ` [PATCH RESEND] scsi: hpsa: Move two variable assignments behind condition checks in hpsa_scsi_ioaccel_raid_map() Markus Elfring
     [not found]   ` <a3329002-827e-d53b-8a4e-860342eb18f7@web.de>
2025-03-03 12:48     ` [PATCH RESEND] drm/mm: Adjust input parameter validation in DECLARE_NEXT_HOLE_ADDR() Markus Elfring
     [not found]   ` <d90b8c11-7a40-eec4-007d-3640c0725a56@web.de>
2025-03-03 13:04     ` [PATCH RESEND] iwlegacy: Adjust input parameter validation in il_set_ht_add_station() Markus Elfring
     [not found]   ` <9cb634c8-d6e6-32bc-5fd6-79bf6b274f96@web.de>
2025-03-03 13:18     ` [PATCH RESEND] iwlwifi: Adjust input parameter validation in iwl_sta_calc_ht_flags() Markus Elfring
2025-03-03 13:46       ` Berg, Benjamin

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