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[51.6.142.41]) by smtp.gmail.com with ESMTPSA id z12sm3468853wrl.48.2020.03.04.10.10.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2020 10:10:19 -0800 (PST) Date: Wed, 4 Mar 2020 18:10:17 +0000 From: Wei Liu To: Lorenzo Pieralisi Cc: Wei Liu , Dexuan Cui , "Gustavo A. R. Silva" , KY Srinivasan , Haiyang Zhang , Stephen Hemminger , Sasha Levin , Andrew Murray , Bjorn Helgaas , "linux-hyperv@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] PCI: hv: Replace zero-length array with flexible-array member Message-ID: <20200304181017.epqvhmtegefb4eba@debian> References: <20200213005048.GA9662@embeddedor.com> <20200304175509.dwhn63omfzewaukv@debian> <20200304180635.GA21844@e121166-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200304180635.GA21844@e121166-lin.cambridge.arm.com> User-Agent: NeoMutt/20180716 Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Wed, Mar 04, 2020 at 06:06:35PM +0000, Lorenzo Pieralisi wrote: > On Wed, Mar 04, 2020 at 05:55:09PM +0000, Wei Liu wrote: > > On Thu, Feb 13, 2020 at 03:43:40AM +0000, Dexuan Cui wrote: > > > > From: linux-hyperv-owner@vger.kernel.org > > > > On Behalf Of Gustavo A. R. Silva > > > > Sent: Wednesday, February 12, 2020 4:51 PM > > > > ... > > > > 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. > > > > > > Looks good to me. Thanks, Gustavo! > > > > > > Reviewed-by: Dexuan Cui > > > > > > > Lorenzo, will you be picking up this patch? It seems to me you've been > > handling patches to pci-hyperv.c. This patch is not yet in pci/hv branch > > in your repository. > > > > Let me know what you think. > > I shall pick it up, I checked patchwork and it was erroneously > assigned to Bjorn, that's why I have not taken it yet. > > Fixed now, apologies, I will merge it shortly. Thanks for picking it up. Wei. > > Lorenzo