From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Zolotarov Subject: Re: [PATCH] ixgbe: fix build with gcc 4.4 Date: Tue, 14 Apr 2015 17:59:37 +0300 Message-ID: <552D2B59.9000907@cloudius-systems.com> References: <1429003900-20074-1-git-send-email-thomas.monjalon@6wind.com> <2601191342CEEE43887BDE71AB9772582141570C@irsmsx105.ger.corp.intel.com> <552D1869.4060703@cloudius-systems.com> <54963304.brPH8sEe9A@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: dev-VfR2kkLFssw@public.gmane.org To: Thomas Monjalon Return-path: In-Reply-To: <54963304.brPH8sEe9A@xps13> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" On 04/14/15 17:17, Thomas Monjalon wrote: > 2015-04-14 16:38, Vlad Zolotarov: >> On 04/14/15 16:06, Ananyev, Konstantin wrote: >>> From: Vlad Zolotarov [mailto:vladz-RmZWMc9puTNJc61us3aD9laTQe2KTcn/@public.gmane.org] >>>> On 04/14/15 12:31, Thomas Monjalon wrote: >>>>> - struct rte_eth_dev_info dev_info = { 0 }; >>>>> + struct rte_eth_dev_info dev_info = { .max_rx_queues = 0 }; >>>> Hmmm... Unless I miss something this and one above would zero only a >>>> single field - "max_rx_queues"; and would leave the rest uninitialized. >>>> The original code intend to zero the whole struct. The alternative to >>>> the original lines could be usage of memset(). >>> As I understand, in that case compiler had to set all non-explicitly initialised members to 0. >>> So I think we are ok here. >> Yeah, I guess it does zero-initializes the rest >> (https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html) however I >> don't understand how the above change fixes the error if it complains >> about the dev_info.driver_name? > As only 1 field is required, I chose the one which should not be removed > from this structure in the future. > >> What I'm trying to say - the proposed fix is completely unclear and >> confusing. Think of somebody reading this line in a month from today - >> he wouldn't get a clue why is it there, why to explicitly set >> max_rx_queues to zero and leave the rest be zeroed automatically... Why >> to add such artifacts to the code instead of just zeroing the struct >> with a memset() and putting a good clear comment above it explaining why >> we use a memset() and not and initializer? > We can make it longer yes. > I think you agree we should avoid extra lines if not needed. > In this case, when reading "= { .field = 0 }", it seems clear our goal > is to zero the structure (it is to me). I'm sorry but it's not clear to me at all since the common C practice for zeroing the struct would be struct st a = {0}; Like in the lines u are changing. The lines as above are clearly should not be commented and are absolutely clear. The lines u are adding on the other hand are absolutely unclear and confusing outside the gcc bug context. Therefore it should be clearly stated so in a form of comment. Otherwise somebody (like myself) may see this and immediately fix it back (as it should be). > I thought it is a basic C practice. I doubt that. ;) Explained above. > > You should try "git grep '\.[^ ]\+ *= *0 *}'" to be convinced that we are > not going to comment each occurence of this coding style. > But it must be explained in the coding style document. Agree? OMG! This is awful! I think everybody agrees that this is a workaround and has nothing to do with a codding style (it's an opposite to a style actually). I don't know where this should be explained, frankly. Getting back to the issue - I'm a bit surprised since I use this kind of initializer ({0}) in a C code for quite a long time - long before 2012. I'd like to understand what is a problem with this specific gcc version. This seems to trivial. I'm surprised CentOS has a gcc version with this kind of bugs.