Re: [RFC][PATCH] Update -Wattribute-alias for gcc9

[Laura Abbott]

On 1/28/19 5:28 AM, Bernd Edlinger wrote:
> On 1/25/19 1:24 PM, Bernd Edlinger wrote:
> > On 1/25/19 12:39 PM, Miguel Ojeda wrote:
> > > On Fri, Jan 25, 2019 at 11:58 AM Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > > > On Fri, Jan 25, 2019 at 11:43 AM Laura Abbott <labbott@xxxxxxxxxx> wrote:
> > > > > Commit bee20031772a ("disable -Wattribute-alias warning for
> > > > > SYSCALL_DEFINEx()") disabled -Wattribute-alias with gcc8.
> > > > > gcc9 changed the format of -Wattribute-alias to take a parameter.
> > > > > This doesn't quite match with the existing disabling mechanism
> > > > > so update for gcc9 to match with the default (-Wattribute-alias=1).
> > > > >
> > > > > Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
> > > > > ---
> > > > > This is RFC because it feels ugly. I went ahead and did the obvious fixup
> > > > > but it's worth discussing if we're going to end up with an explosion or
> > > > > if there's a better way to handle this in one macro.
> > > >
> > > > Bernd Edlinger has sent a patch to gcc for this:
> > > > https://gcc.gnu.org/ml/gcc-patches/2019-01/msg01120.html
> > > >
> > > > and Miguel Ojeda said he wanted to send a patch for it to the
> > > > kernel as well, not sure if he wanted to take a different
> > > > approach there, so adding both to Cc here.
> > >
> > > Thanks Arnd (I was working with Martin on the expanded
> > > -Wmissing-attribute warnings, not on this, but thanks nevertheless :).
> > >
> > > Martin/Bernd: from the GCC mailing list I am not sure if we should
> > > expect the old behavior to be maintained or not.
> >
> > I believe it is not intentional to break the old syntax of the
> > pragma.  There will be new -Wattribute-alias=1 and -Wattribute-alias=2
> > and -Wattribute-alias is easy to retain as an alias for -Wattribute-alias=1.
> > That is what my patch will do.
>
> Okay, I committed the -Wattribute-alias patch to gcc trunk, now
> as https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=268336 .
> So there will be no need for a workaround on your side.
>
> Also fixed a few false positive -Waddress-of-packed-member warnings with
> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=268118 and
> https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=268337 .
>
> However there remain a lot of warnings from -Waddress-of-packed-member,
> that look more or less valid, has anybody an idea how to handle
> these?
>
>
> Bernd.

Thanks, I'll keep an eye out when this lands in Fedora gcc.
I think once everything lands it will be easier to work on
the remaining -Waddress-of-packed-member.

Laura