[Freeipa-devel] C coding style guide update

[Petr Vobornik]

On 07/26/2015 10:09 PM, Jakub Hrozek wrote:
> On Thu, Jul 23, 2015 at 06:21:25PM +0200, Michal Židek wrote:
>> Hi,
>>
>> in SSSD we use the freeipa coding guidelines which are located here:
>> http://www.freeipa.org/page/Coding_Style
>>
>> However this coding style guide is already dated and there are
>> some rules we follow in SSSD which are not mentioned in the guide
>> and also there are some C language features that we would like to
>> start using in certain way but their usage should be covered in the
>> coding style guide. So, update is needed (at least for SSSD).
>>
>> I would like to start discussion about what to add to the coding
>> guide (and maybe what to remove), but before that, I would like
>> propose to move the coding style guide to SSSD wiki and just add link
>> to it to FreeIPA wiki. The reason is that unlike FreeIPA, most of the
>> SSSD code is written in C and SSSD team will more likely update and
>> modify the guide according to new practices used in upstream
>> development, where FreeIPA is mostly Python project and C coding
>> style probably does not need revision as often. So SSSD wiki
>> seems like more appropriate place.
>>
>> Another possibility would be to fork the FreeIPA style and
>> maintain SSSD coding style guide separately. But I think linking
>> the two is better option, because the two projects are closely
>> related and it makes sense to share the coding style guidelines.
>>
>> So, my first question is, Is someone against moving the C coding
>> style guide to SSSD wiki and adding link to it on FreeIPA wiki?
>
> I don't really mind where the coding style is located as long as it's
> on one place (no forks please) and the existing link points to a new
> version (if any).
>
> As per updating the coding standards, I would like to propose to:
>      - explicitly say that C99 is fine to use. It's 2015 and any compiler
>        that doesn't support C99 at this point is probably dead and should
>        be avoided (Hello, MSVC!). We use stdbool.h and variadic macros
>        already anyway.
>      - Line-comments (//, aka C++ comments) should be still avoided,
>        though
>      - Variable Length arrays are very helpful, but explicitly mention
>        they should be used with caution, especially if array size might
>        come from the user
>      - Also, I would warn about interleaved variable declarations. I
>        think it's fine to declare some helper variable inside a for loop
>        for example, but generally it might be better to refactor the
>        function if we find out there's so many variables that the code
>        author ends up declaring them inside blocks.
>
> Personally, I would even go as far as to allow the __cleanup__
> attribute. I really like how the systemd codebase uses it to define
> helper "destructors" like:
>      int closep(int fd)
>      {
>          if (fd >= 0) {
>              close(fd);
>          }
>      }
>
>      #define _cleanup_close_ _cleanup_(closep)
>
> Then safely declare a file descriptor as:
>      _cleanup_close_ int fdf = -1;
> ..and stop worrying about closing the fd in all branches.
>
> It's not portable, but seriously...are there any compilers except gcc
> and clang that are used at all these days??
>

Location of the C coding style guide was discussed on FreeIPA dev call. 
Conclusion was the same as Jakub's opinion: no fork, link from the 
other, it doesn't matter if it is in SSSD or FreeIPA wiki.
-- 
Petr Vobornik