From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Subject: Re: [PATCH 4/11] use ether_addr_equal_64bits Date: Tue, 31 Dec 2013 17:40:24 +0100 (CET) Message-ID: References: <1388427307-8691-1-git-send-email-Julia.Lawall@lip6.fr> <1388427307-8691-5-git-send-email-Julia.Lawall@lip6.fr> <1388429761.4410.1.camel@jlt4.sipsolutions.net> <1388438724.4573.2.camel@jlt4.sipsolutions.net> <20131230215701.GA4938@khazad-dum.debian.net> <1388445188.18164.0.camel@jlt4.sipsolutions.net> <1388445422.26796.38.camel@joe-AO722> <52C2E8BA.6000800@candelatech.com> <52C2F056.1020005@candelatech.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Julia Lawall , Joe Perches , Johannes Berg , Henrique de Moraes Holschuh , kernel-janitors@vger.kernel.org, Emmanuel Grumbach , Intel Linux Wireless , "John W. Linville" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Ben Greear Return-path: In-Reply-To: <52C2F056.1020005@candelatech.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 31 Dec 2013, Ben Greear wrote: > On 12/31/2013 08:09 AM, Julia Lawall wrote: > > > > > > On Tue, 31 Dec 2013, Ben Greear wrote: > > > > > On 12/30/2013 10:32 PM, Julia Lawall wrote: > > > > > > > > I'm just thinking of a programmer, e.g. changing a struct like > > > > > > > > this: > > > > > > > > > > > > > > > > struct foo { > > > > > > > > u8 addr[ETH_ALEN]; > > > > > > > > - u16 dummy; > > > > > > > > }; > > > > > > > > > > I don't know of a way to catch that. > > > > > Anyone else? > > > > > > > > Well, one could have a semantic patch that checks for that. But the > > > > problem is that it is very slow, and it only covers the cases that I can > > > > transform automatically, which currently means no pointers, only > > > > explicit > > > > arrays. > > > > > > > > On the other hand, I am finding the structure definition, so I can > > > > easily > > > > update the structure definition with an appropriate comment. > > > > > > > > struct foo { > > > > u8 addr[ETH_ALEN]; /* must be followed by two bytes in the > > > > structure */ > > > > u16 dummy; > > > > }; > > > > > > > > Unfortunately it is kind of verbose. Could there be an attribute? That > > > > could even easily be checked. > > > > > > Can you not just add a build-time macro to check that sizeof(foo) >= 8 > > > for each of these struct foos? Or, is it required that the dummy field > > > be there and be not used by anything else? > > > > It doesn't matter what the field is used for. The problem is that is it > > necessary to ensure a property of the position of addr within the > > structure. It has to have at least 16 bytes after it. > > You mean 16 bits? Oops, yes. 16 bits. > > > > But maybe something with sizeof(foo) and offset_of would do? > > > > Could the macro be put near the declaration of the structure somehow? > > I think that would work, but do not know all of the details of such > macros, so it's possible there is some catch. > > If nothing else, then some run-time code that calculates the offset off > and asserts if it is broken in module initialization or similar might > be good enough. Could be OK. Something right in or after the structure declaration would be nicest. julia > > Thanks, > Ben > > -- > Ben Greear > Candela Technologies Inc http://www.candelatech.com > > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >