Re: [PATCH] reboot: Fix variable assignments in type_store

[Matteo Croce]

On Thu, Nov 12, 2020 at 6:49 PM Nathan Chancellor
<natechancellor@xxxxxxxxx> wrote:
>
> Hi Matteo,
>
> On Thu, Nov 12, 2020 at 12:26:45PM +0100, Matteo Croce wrote:
> > On Thu, Nov 12, 2020 at 4:50 AM Nathan Chancellor
> > <natechancellor@xxxxxxxxx> wrote:
> > >
> > > Clang warns:
> > >
> > > kernel/reboot.c:707:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_TRIPLE;
> > >                             ~ ^~~~~~~~~~~
> > > kernel/reboot.c:709:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_KBD;
> > >                             ~ ^~~~~~~~
> > > kernel/reboot.c:711:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_BIOS;
> > >                             ~ ^~~~~~~~~
> > > kernel/reboot.c:713:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_ACPI;
> > >                             ~ ^~~~~~~~~
> > > kernel/reboot.c:715:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_EFI;
> > >                             ~ ^~~~~~~~
> > > kernel/reboot.c:717:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_CF9_FORCE;
> > >                             ~ ^~~~~~~~~~~~~~
> > > kernel/reboot.c:719:17: warning: implicit conversion from enumeration
> > > type 'enum reboot_type' to different enumeration type 'enum reboot_mode'
> > > [-Wenum-conversion]
> > >                 reboot_mode = BOOT_CF9_SAFE;
> > >                             ~ ^~~~~~~~~~~~~
> > > 7 warnings generated.
> > >
> > > It seems that these assignment should be to reboot_type, not
> > > reboot_mode. Fix it so there are no more warnings and the code works
> > > properly.
> > >
> > > Fixes: eab8da48579d ("reboot: allow to specify reboot mode via sysfs")
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/1197
> > > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> > > ---
> > >  kernel/reboot.c | 14 +++++++-------
> > >  1 file changed, 7 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/kernel/reboot.c b/kernel/reboot.c
> > > index deba133a071b..8599d0d44aec 100644
> > > --- a/kernel/reboot.c
> > > +++ b/kernel/reboot.c
> > > @@ -704,19 +704,19 @@ static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
> > >                 return -EPERM;
> > >
> > >         if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
> > > -               reboot_mode = BOOT_TRIPLE;
> > > +               reboot_type = BOOT_TRIPLE;
> > >         else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
> > > -               reboot_mode = BOOT_KBD;
> > > +               reboot_type = BOOT_KBD;
> > >         else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
> > > -               reboot_mode = BOOT_BIOS;
> > > +               reboot_type = BOOT_BIOS;
> > >         else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
> > > -               reboot_mode = BOOT_ACPI;
> > > +               reboot_type = BOOT_ACPI;
> > >         else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
> > > -               reboot_mode = BOOT_EFI;
> > > +               reboot_type = BOOT_EFI;
> > >         else if (!strncmp(buf, BOOT_CF9_FORCE_STR, strlen(BOOT_CF9_FORCE_STR)))
> > > -               reboot_mode = BOOT_CF9_FORCE;
> > > +               reboot_type = BOOT_CF9_FORCE;
> > >         else if (!strncmp(buf, BOOT_CF9_SAFE_STR, strlen(BOOT_CF9_SAFE_STR)))
> > > -               reboot_mode = BOOT_CF9_SAFE;
> > > +               reboot_type = BOOT_CF9_SAFE;
> > >         else
> > >                 return -EINVAL;
> > >
> > >
> > > base-commit: 3e14f70c05cda4794901ed8f976de3a88deebcc0
> > > --
> > > 2.29.2
> > >
> >
> > Hmm, this was introduced in v3 I think.
> >
> > I wonder why my compiler doesn't warn about it, the two variables are
> > defined as different enum type.
> > I get the same warnings with GCC and -Wenum-conversion.
>
> What version of GCC do you have? -Wenum-conversion is a fairly new
> warning in GCC I think. Although if you get it now, maybe it was some
> configuration error?
>

Hi,

the one shipped in Fedora 33:
gcc version 10.2.1 20201016 (Red Hat 10.2.1-6) (GCC)

I enabled -Wenum-compare -Wenum-conversion globally in the root
Makefile and I had only 15 warnings for an 'allyesconfig' x86_64
build.

Maybe it's worth fixing them and enable the warning, it's very useful.

Thanks,
-- 
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