Re: [PATCH RESEND] selftests: Suppress unused variable warning

[John Hubbard]

On 6/19/25 10:00 AM, Shuah Khan wrote:
> On 6/19/25 01:46, Chen Linxuan wrote:
> > On Thu, Jun 19, 2025 at 5:23 AM Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> 
> > wrote:
> > > On 6/9/25 20:07, Chen Linxuan wrote:
...
> > > > diff --git a/tools/testing/selftests/filesystems/mount-notify/mount- 
> > > > notify_test.c b/tools/testing/selftests/filesystems/mount-notify/ 
> > > > mount-notify_test.c
> > > > index 63ce708d93ed0..34afe27b7978f 100644
> > > > --- a/tools/testing/selftests/filesystems/mount-notify/mount- 
> > > > notify_test.c
> > > > +++ b/tools/testing/selftests/filesystems/mount-notify/mount- 
> > > > notify_test.c
> > > > @@ -465,7 +465,9 @@ TEST_F(fanotify, rmdir)
> > > >        ASSERT_GE(ret, 0);
> > > >
> > > >        if (ret == 0) {
> > > > -             chdir("/");
> > > > +             // Suppress -Wunused-result
> > > > +             // Ref: https://gcc.gnu.org/bugzilla/show_bug.cgi? 
> > > > id=66425#c34
> > > > +             (void) !chdir("/");

This is quite ugly. :)

> > > > > Why not fix the problem the right way by checking the return value.
> > > Suppressing the error isn't useful.
> >
> > The code is already handling cleanup in error cases,
> > and I don't think checking the result of chdir would be useful here.

Why not just fail with the appropriate test result, if chdir() fails
here, instead of making a bit of a mess with odd void casts to a
negated return value, and a reference to a compiler bug report?

Really, Shuah is putting you on the right path here.

> We check for chdir() in several tools in the kernel. Add a check for
> it instead of suppressing the [-Wunused-result] - suppressing doesn't
> do any good.
>
> thanks,
> -- Shuah

thanks,
--
John Hubbard