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[85.228.170.18]) by smtp.gmail.com with ESMTPSA id d24sm7300090lja.82.2020.02.25.00.45.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2020 00:45:01 -0800 (PST) Received: from johan by xi.terra with local (Exim 4.92.3) (envelope-from ) id 1j6Vpp-0004Ni-IX; Tue, 25 Feb 2020 09:44:57 +0100 Date: Tue, 25 Feb 2020 09:44:57 +0100 From: Johan Hovold To: "Gustavo A. R. Silva" Cc: Greg Kroah-Hartman , Minas Harutyunyan , Alan Stern , Thierry Reding , Jonathan Hunter , Mathias Nyman , Matthias Brugger , Johan Hovold , Felipe Balbi , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] USB: Replace zero-length array with flexible-array member Message-ID: <20200225084457.GO32540@localhost> References: <20200220132017.GA29262@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200220132017.GA29262@embeddedor> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Feb 20, 2020 at 07:20:17AM -0600, Gustavo A. R. Silva wrote: > The current codebase makes use of the zero-length array language > extension to the C90 standard, but the preferred mechanism to declare > variable-length types such as these ones is a flexible array member[1][2], > introduced in C99: > > struct foo { > int stuff; > struct boo array[]; > }; > > By making use of the mechanism above, we will get a compiler warning > in case the flexible array does not occur last in the structure, which > will help us prevent some kind of undefined behavior bugs from being > inadvertently introduced[3] to the codebase from now on. > > Also, notice that, dynamic memory allocations won't be affected by > this change: > > "Flexible array members have incomplete type, and so the sizeof operator > may not be applied. As a quirk of the original implementation of > zero-length arrays, sizeof evaluates to zero."[1] > > This issue was found with the help of Coccinelle. > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > [2] https://github.com/KSPP/linux/issues/21 > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > > Signed-off-by: Gustavo A. R. Silva > --- > drivers/usb/atm/usbatm.h | 2 +- > drivers/usb/dwc2/hcd.h | 2 +- > drivers/usb/host/ehci-tegra.c | 2 +- > drivers/usb/host/ehci.h | 4 ++-- > drivers/usb/host/fotg210.h | 2 +- > drivers/usb/host/ohci.h | 4 ++-- > drivers/usb/host/xhci-mtk.h | 2 +- > drivers/usb/host/xhci.h | 4 ++-- > drivers/usb/serial/io_usbvend.h | 4 ++-- > drivers/usb/serial/ti_usb_3410_5052.c | 4 ++-- > include/linux/usb.h | 4 ++-- > include/linux/usb/audio-v2.h | 2 +- > include/linux/usb/audio-v3.h | 2 +- > include/linux/usb/gadget.h | 2 +- > include/linux/usb/hcd.h | 2 +- > include/linux/usbdevice_fs.h | 2 +- > 16 files changed, 22 insertions(+), 22 deletions(-) Looks like your scripts still doesn't catch every instance. A simple grep like git grep -A1 '\[0\];$' drivers/usb/ | grep -B1 '}' found at least three more in drivers/usb/atm/ueagle-atm.c drivers/usb/gadget/function/f_phonet.c drivers/usb/musb/musb_host.c Johan