2015-04-14 18:21, Vlad Zolotarov: > > On 04/14/15 18:13, Thomas Monjalon wrote: > > 2015-04-14 17:59, Vlad Zolotarov: > >> 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 at cloudius-systems.com] > >>>>>> 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. > > Once we assert we want to support this buggy compiler, the workarounds > > are automatically parts of the coding style. > > It'd rather not... ;) > > > I don't know how to deal differently with this constraint. > > Add -Wno-missing-braces compilation option for compiler versions below > 4.7. U (and me and I guess most other developers) compile DPDK code with > a newer compiler thus the code would be properly inspected with these > compilers and we may afford to be less restrictive with compilation > warnings with legacy compiler versions...
You're right. I will test it and submit a v2. Then I could use the above grep command to replace other occurences of this workaround. > >> 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. > > Each day brings its surprise :)