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R. Silva" Cc: Daniel Drake , Ulrich Kunitz , "David S. Miller" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH][next] zd1211rw/zd_usb.h: Replace zero-length array with flexible-array member References: <20200305111216.GA24982@embeddedor> Date: Thu, 05 Mar 2020 16:50:03 +0200 In-Reply-To: <20200305111216.GA24982@embeddedor> (Gustavo A. R. Silva's message of "Thu, 5 Mar 2020 05:12:16 -0600") Message-ID: <87k13yq2jo.fsf@kamboji.qca.qualcomm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org "Gustavo A. R. Silva" writes: > 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/net/wireless/zydas/zd1211rw/zd_usb.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) "zd1211rw: " is enough, no need to have the filename in the title. But I asked this already in an earlier patch, who prefers this format? It already got opposition so I'm not sure what to do. -- https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches