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

From: Laura Abbott
Date: Mon Jan 28 2019 - 09:35:31 EST


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