[dpdk-dev] [PATCH] net/mlx: fix compile errors with ignore pedantic pragma

[Ferruh Yigit]

On 9/20/2016 7:17 PM, Adrien Mazarguil wrote:
> On Tue, Sep 20, 2016 at 04:58:48PM +0100, Bruce Richardson wrote:
>> On Tue, Sep 20, 2016 at 02:51:27PM +0200, Adrien Mazarguil wrote:
>>> On Mon, Sep 19, 2016 at 04:26:05PM +0100, Bruce Richardson wrote:
>>>> On Mon, Sep 19, 2016 at 04:59:59PM +0200, Adrien Mazarguil wrote:
>>>>> Hi Bruce,
>>>>>
>>>>> On Mon, Sep 19, 2016 at 03:36:54PM +0100, Bruce Richardson wrote:
>>>>>> With recent gcc versions, e.g. gcc 6.1, compilation of mlx drivers with
>>>>>> debug enabled produces lots of errors complaining that "pedantic" is
>>>>>> not a warning level that can be ignored.
>>>>>>
>>>>>> error: ‘-pedantic’ is not an option that controls warnings [-Werror=pragmas]
>>>>>>  #pragma GCC diagnostic ignored "-pedantic"
>>>>>>                                  ^~~~~~~~~~~
>>>>>>
>>>>>> These errors can be removed by changing the "-pedantic" to "-Wpedantic".
>>>>>
>>>>> Nice to have a workaround, I thought they did not keep the option at all.
>>>>> However after testing:
>>>>>
>>>>> - It does not seem to work with GCC 4.6 and older, they prefer -pedantic:
>>>>>   "warning: unknown option after `#pragma GCC diagnostic' kind".
>>>>>
>>>>> - GCC 4.9 (possibly 5.x as well) does not care, can use either -pedantic or
>>>>>   -Wpedantic.
>>>>>
>>>>> - GCC 6 can only supports -Wpedantic.
>>>>>
>>>>> Note we're working toward removing the need for these #pragma in the first
>>>>> place as soon as possible, however in the meantime I fear that checking the
>>>>> GCC version is necessary.
>>>>>
>>>> Depends on how old of GCC version we need to support. From the release notes
>>>> it appears that -Wpedantic was introduced in GCC 4.8 (3 1/2 years ago).
>>>>
>>>> https://gcc.gnu.org/gcc-4.8/changes.html
>>>>
>>>> Do we need to support compilation on gcc versions older than this?
>>>
>>> I'm all for upgrading so I do not really mind if we stop caring about older
>>> GCC versions (especially considering this problem only occurs in debugging
>>> mode which is seldom used by non-developers). The version check is necessary
>>> if we want to keep full compatibility with at least:
>>>
>>> - RHEL <= 6.x
>>> - Debian <= 7.x
>>> - Ubuntu <= 13.04
>>>
>>> Works for me either way, thus:
>>>
>>> Acked-by: Adrien Mazarguil <adrien.mazarguil at 6wind.com>
>>>
>> Any objections to dropping of support for debug settings for these OS's?
> 
> Not sure who should answer this. These #pragma are workarounds we should
> eventually get rid of anyway (DPDK headers are now clean enough, some work
> remains to be done on the Verbs side) so let's use your patch in the
> meantime.
> 

Just as a quick note, this breaks compilation for ICC:

.../drivers/net/mlx4/mlx4.c(64): error #2282: unrecognized GCC pragma
  #pragma GCC diagnostic ignored "-Wpedantic"

Since this compilation error only happens for MLX4/5 when debug config
option enabled, this not big issue, but please aware of the issue.

Thanks,
ferruh