Re: [Xen-devel] Lots of new warnings with gcc-7.1.1

[Arnd Bergmann <arnd@xxxxxxxx>]

On Wed, Jul 12, 2017 at 3:10 PM, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Jul 11, 2017 at 03:35:15PM -0700, Linus Torvalds wrote:
>> [ Very random list of maintainers and mailing lists, at least
>> partially by number of warnings generated by gcc-7.1.1 that is then
>> correlated with the get_maintainers script ]
>>
>> So I upgraded one of my boxes to F26, which upgraded the compiler to 
>> gcc-7.1.1
>>
>> Which in turn means that my nice clean allmodconfig compile is not an
>> unholy mess of annoying new warnings.
>
> I asked Arnd about this the other day on IRC as I've hit this as well on
> the stable releases, and it's really annoying.  He mentioned that he had
> lots of these warnings fixed, but didn't push most of the changes out
> yet.

To clarify: most of the patches I wrote ended up getting merged, but
there were a couple that I did not submit a second time after they
got dropped, but I gave up on trying to fix the new -Wformat warnings
and simply disabled them, hoping someone else would do it before me,
or that the gcc developers would find a way to reduce the false-positive
ones before the release.

>  Arnd, any repo with them in it that we could look at?

I have a private tree on my workstation that has lots of random
crap, and I rebase it all the time but normally don't publish it.

I have uploaded today's snapshot to

git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git randconfig-4.13-next

The way I work with this is helpful to catch build regressions as soon
as they happen, but not so good in finding things that I have either
submitted a patch for before and don't remember if it should be
resubmitted, or stuff that I decided I didn't want to deal with at some
point.

I was already planning to start over from scratch one of these days,
and cherry-pick+resubmit the patches that are actually required
for randconfig builds.

>> Anyway, it would be lovely if some of the more affected developers
>> would take a look at gcc-7.1.1 warnings. Right now I get about three
>> *thousand* lines of warnings from a "make allmodconfig" build, which
>> makes them a bit overwhelming.
>
> I only have 310 when building the 4.12.0 release with 7.1.1, I wonder if
> Fedora turned more warnings on in their compiler release, I'm running
> Arch here:
>         $ gcc --version
>         gcc (GCC) 7.1.1 20170621

This is what I get in today's linux-next:

$ grep error: 4.13-next-allmod-warning | sed -e 's:^.*\[-W:-W:' | sort
| uniq -c | cut -f 1 -d\] | sort -n
      1 -Werror=parentheses
      2 -Werror=tautological-compare
      2 -Werror=unused-result
     34 -Werror=format-overflow=
     41 -Werror=int-in-bool-context
    233 -Werror=format-truncation=

I'll resubmit the patches for -Wparenthese, -Wtautological-compar,
-Wunused-result and -Wint-in-bool-context that I had sent earlier,
plus a new patch to move -Wformat-truncation into W=1.

      Arnd

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