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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b78d45d152sm3585536f8f.3.2025.07.29.05.59.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Jul 2025 05:59:47 -0700 (PDT) Message-ID: <15536eea-5a66-4dff-b4bd-8a43fbfa9365@linaro.org> Date: Tue, 29 Jul 2025 14:59:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hw/display/xenfb: Replace unreachable code by abort() To: Markus Armbruster Cc: qemu-devel@nongnu.org, sstabellini@kernel.org, anthony@xenproject.org, paul@xen.org, edgar.iglesias@gmail.com, xen-devel@lists.xenproject.org, qemu-trivial@nongnu.org References: <20250729111226.3627499-1-armbru@redhat.com> <14fff91b-7434-4d90-adb1-ebbe3f51d605@linaro.org> <87v7nbdwfx.fsf@pond.sub.org> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <87v7nbdwfx.fsf@pond.sub.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::332; envelope-from=philmd@linaro.org; helo=mail-wm1-x332.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 29/7/25 14:16, Markus Armbruster wrote: > Philippe Mathieu-Daudé writes: > >> On 29/7/25 13:12, Markus Armbruster wrote: >>> xenfb_mouse_event() has a switch statement whose controlling >>> expression move->axis is an enum InputAxis. The enum values are >>> INPUT_AXIS_X and INPUT_AXIS_Y, encoded as 0 and 1. The switch has a >>> case for both axes. In addition, it has an unreachable default label. >>> This convinces Coverity that move->axis can be greater than 1. It >>> duly reports a buffer overrun when it is used to subscript an array >>> with two elements. >>> Replace the unreachable code by abort(). >>> Resolves: Coverity CID 1613906 >>> Signed-off-by: Markus Armbruster >>> --- >>> hw/display/xenfb.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c >>> index 22822fecea..5e6c691779 100644 >>> --- a/hw/display/xenfb.c >>> +++ b/hw/display/xenfb.c >>> @@ -283,8 +283,7 @@ static void xenfb_mouse_event(DeviceState *dev, QemuConsole *src, >>> scale = surface_height(surface) - 1; >>> break; >>> default: >>> - scale = 0x8000; >>> - break; >>> + abort(); >> >> We prefer GLib g_assert_not_reached() over abort() because it displays >> the file, line number & function before aborting. > > The purpose of this line is to tell the compiler we can't get there, > with the least amount of ceremony. > > We have ~600 calls of abort(). And ~1600 of g_assert_not_reached() =) $ git grep -w 'abort();' | wc -l 556 $ git grep -w 'g_assert_not_reached();' | wc -l 1551 > Whoever merges this: feel free to replace by g_assert_not_reached(). > >>> } >>> xenfb->axis[move->axis] = move->value * scale / 0x7fff; >>> } >