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

[Panu Matilainen <pmatilai@redhat.com>]

----- Original Message -----
> 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@6wind.com>
> > 
> Any objections to dropping of support for debug settings for these OS's?

No objections on dropping RHEL <= 6 support, we never did DPDK on those old
versions anyway.

As for the others, I've no particular opinion but certainly no objections
either.

   - Panu -

> 
> /Bruce
>