Re: [PATCH] scsi: st: Add missing break in switch statement in st_ioctl()

[Nathan Chancellor]

On 8/17/2021 5:54 PM, Finn Thain wrote:
> On Tue, 17 Aug 2021, Nathan Chancellor wrote:
>
> > Clang + -Wimplicit-fallthrough warns:
> >
> > drivers/scsi/st.c:3831:2: warning: unannotated fall-through between
> > switch labels [-Wimplicit-fallthrough]
> >          default:
> >          ^
> > drivers/scsi/st.c:3831:2: note: insert 'break;' to avoid fall-through
> >          default:
> >          ^
> >          break;
> > 1 warning generated.
> >
> > Clang's -Wimplicit-fallthrough is a little bit more pedantic than GCC's,
> > requiring every case block to end in break, return, or fallthrough,
> > rather than allowing implicit fallthroughs to cases that just contain
> > break or return. Add a break so that there is no more warning, as has
> > been done all over the tree already.
> >
> > Fixes: 2e27f576abc6 ("scsi: scsi_ioctl: Call scsi_cmd_ioctl() from scsi_ioctl()")
> > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> > ---
> >   drivers/scsi/st.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
> > index 2d1b0594af69..0e36a36ed24d 100644
> > --- a/drivers/scsi/st.c
> > +++ b/drivers/scsi/st.c
> > @@ -3828,6 +3828,7 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
> >   	case CDROM_SEND_PACKET:
> >   		if (!capable(CAP_SYS_RAWIO))
> >   			return -EPERM;
> > +		break;
> >   	default:
> >   		break;
> >   	}
> >
> > base-commit: 58dd8f6e1cf8c47e81fbec9f47099772ab75278b
>
> Well, that sure is ugly.
>
> Do you think the following change would cause any static checkers to spit
> their dummys and throw their toys out of the pram?
>
> @@ -3828,6 +3828,7 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
>   	case CDROM_SEND_PACKET:
>   		if (!capable(CAP_SYS_RAWIO))
>   			return -EPERM;
> +		break;
> -	default:
> -		break;
>   	}
>   	

I cannot speak for other static checkers but clang does not complain in 
this instance. cmd_in is the switch value, which is unsigned int; as far 
as I am aware, clang will only complain about a switch not handling all 
values when switching on an enumerated type.

Gustavo, if you are already handling all of the other warnings in -next, 
do you want to take this one too?

Cheers,
Nathan