| Message ID | 20190228202759.GA5883@embeddedor (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [v2] scsi: NCR5380: Mark expected switch fall-through | expand |
On Thu, 28 Feb 2019, Gustavo A. R. Silva wrote: > In preparation to enabling -Wimplicit-fallthrough, mark switch > cases where we are expecting to fall through. > This switch case is already marked. So I think the patch description should state that this patch is actually a workaround for a gcc deficiency which prevents it from locating the marker. > This patch fixes the following warning: > > In file included from drivers/scsi/dmx3191d.c:48: > drivers/scsi/NCR5380.c: In function ?NCR5380_information_transfer?: > drivers/scsi/NCR5380.c:1933:9: warning: this statement may fall through [-Wimplicit-fallthrough=] > if (!hostdata->connected) > ^ > drivers/scsi/NCR5380.c:1937:5: note: here > default: > ^~~~~~~ > > Warning level 3 was used: -Wimplicit-fallthrough=3 > > Notice that, in this particular case, the code comment is modified > in accordance with what GCC is expecting to find. > > This patch is part of the ongoing efforts to enable > -Wimplicit-fallthrough. > > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> > --- > Changes in v2: > - Update commit log. > - Move code comment after the default label and > retain reason for fall-through in comment as > requested by Michael Schmitz. > > drivers/scsi/NCR5380.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c > index 01c23d27f290..985d1c053578 100644 > --- a/drivers/scsi/NCR5380.c > +++ b/drivers/scsi/NCR5380.c > @@ -1933,13 +1933,12 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) > if (!hostdata->connected) > return; > > - /* Fall through to reject message */ > - > + /* Fall through - to reject message */ This new hyphen is wrong and harms readability for humans. I did confirm that gcc can be appeased by the use of a hyphen but not by correct grammar such as "Fall through to reject message" or "Fall through. Reject message." > + default: > /* > - * If we get something weird that we aren't expecting, > - * reject it. > + * If we get something weird that we > + * aren't expecting, reject it. This reformatting isn't relevant to this patch. The comments can be improved however (see below). > */ > - default: Moving the 'default' keyword closer to the 'fall through' comment makes sense to me -- I could understand if gcc had simple, unambiguous rules for annotations. Do compilers and static analysers agree as to what a correctly annotated switch label should look like? If not, we would have to try to mangle code and comments in such a way that might satisfy all of the failings in all of the tools. > if (tmp == EXTENDED_MESSAGE) > scmd_printk(KERN_INFO, cmd, > "rejecting unknown extended message code %02x, length %d\n", > Here's an alternative patch, which has the virtue that a simple heuristic will work. This patch does not require that other static analysis tools will follow gcc's weird rules about hyphens. (I assume they don't but I didn't check.) diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c index 7fed9bb72784..fe0535affc14 100644 --- a/drivers/scsi/NCR5380.c +++ b/drivers/scsi/NCR5380.c @@ -1932,13 +1932,13 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) if (!hostdata->connected) return; - /* Fall through to reject message */ - + /* Reject message */ + /* Fall through */ + default: /* * If we get something weird that we aren't expecting, - * reject it. + * log it. */ - default: if (tmp == EXTENDED_MESSAGE) scmd_printk(KERN_INFO, cmd, "rejecting unknown extended message code %02x, length %d\n", --
Finn's version looks fine to me. Cheers, Michael On 1/03/19 2:16 PM, Finn Thain wrote: > On Thu, 28 Feb 2019, Gustavo A. R. Silva wrote: > >> In preparation to enabling -Wimplicit-fallthrough, mark switch >> cases where we are expecting to fall through. >> > This switch case is already marked. So I think the patch description > should state that this patch is actually a workaround for a gcc deficiency > which prevents it from locating the marker. > >> This patch fixes the following warning: >> >> In file included from drivers/scsi/dmx3191d.c:48: >> drivers/scsi/NCR5380.c: In function ?NCR5380_information_transfer?: >> drivers/scsi/NCR5380.c:1933:9: warning: this statement may fall through [-Wimplicit-fallthrough=] >> if (!hostdata->connected) >> ^ >> drivers/scsi/NCR5380.c:1937:5: note: here >> default: >> ^~~~~~~ >> >> Warning level 3 was used: -Wimplicit-fallthrough=3 >> >> Notice that, in this particular case, the code comment is modified >> in accordance with what GCC is expecting to find. >> >> This patch is part of the ongoing efforts to enable >> -Wimplicit-fallthrough. >> >> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> >> --- >> Changes in v2: >> - Update commit log. >> - Move code comment after the default label and >> retain reason for fall-through in comment as >> requested by Michael Schmitz. >> >> drivers/scsi/NCR5380.c | 9 ++++----- >> 1 file changed, 4 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c >> index 01c23d27f290..985d1c053578 100644 >> --- a/drivers/scsi/NCR5380.c >> +++ b/drivers/scsi/NCR5380.c >> @@ -1933,13 +1933,12 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) >> if (!hostdata->connected) >> return; >> >> - /* Fall through to reject message */ >> - >> + /* Fall through - to reject message */ > This new hyphen is wrong and harms readability for humans. > > I did confirm that gcc can be appeased by the use of a hyphen but not by > correct grammar such as "Fall through to reject message" or "Fall through. > Reject message." > >> + default: >> /* >> - * If we get something weird that we aren't expecting, >> - * reject it. >> + * If we get something weird that we >> + * aren't expecting, reject it. > This reformatting isn't relevant to this patch. The comments can be > improved however (see below). > >> */ >> - default: > Moving the 'default' keyword closer to the 'fall through' comment makes > sense to me -- I could understand if gcc had simple, unambiguous rules for > annotations. > > Do compilers and static analysers agree as to what a correctly annotated > switch label should look like? If not, we would have to try to mangle code > and comments in such a way that might satisfy all of the failings in all > of the tools. > >> if (tmp == EXTENDED_MESSAGE) >> scmd_printk(KERN_INFO, cmd, >> "rejecting unknown extended message code %02x, length %d\n", >> > Here's an alternative patch, which has the virtue that a simple heuristic > will work. This patch does not require that other static analysis tools > will follow gcc's weird rules about hyphens. (I assume they don't but I > didn't check.) > > diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c > index 7fed9bb72784..fe0535affc14 100644 > --- a/drivers/scsi/NCR5380.c > +++ b/drivers/scsi/NCR5380.c > @@ -1932,13 +1932,13 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) > if (!hostdata->connected) > return; > > - /* Fall through to reject message */ > - > + /* Reject message */ > + /* Fall through */ > + default: > /* > * If we get something weird that we aren't expecting, > - * reject it. > + * log it. > */ > - default: > if (tmp == EXTENDED_MESSAGE) > scmd_printk(KERN_INFO, cmd, > "rejecting unknown extended message code %02x, length %d\n", >
Hi Finn, Please submit this as a formal patch. Thanks! > Here's an alternative patch, which has the virtue that a simple heuristic > will work. This patch does not require that other static analysis tools > will follow gcc's weird rules about hyphens. (I assume they don't but I > didn't check.) > > diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c > index 7fed9bb72784..fe0535affc14 100644 > --- a/drivers/scsi/NCR5380.c > +++ b/drivers/scsi/NCR5380.c > @@ -1932,13 +1932,13 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) > if (!hostdata->connected) > return; > > - /* Fall through to reject message */ > - > + /* Reject message */ > + /* Fall through */ > + default: > /* > * If we get something weird that we aren't expecting, > - * reject it. > + * log it. > */ > - default: > if (tmp == EXTENDED_MESSAGE) > scmd_printk(KERN_INFO, cmd, > "rejecting unknown extended message code %02x, length %d\n",
diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c index 01c23d27f290..985d1c053578 100644 --- a/drivers/scsi/NCR5380.c +++ b/drivers/scsi/NCR5380.c @@ -1933,13 +1933,12 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) if (!hostdata->connected) return; - /* Fall through to reject message */ - + /* Fall through - to reject message */ + default: /* - * If we get something weird that we aren't expecting, - * reject it. + * If we get something weird that we + * aren't expecting, reject it. */ - default: if (tmp == EXTENDED_MESSAGE) scmd_printk(KERN_INFO, cmd, "rejecting unknown extended message code %02x, length %d\n",
In preparation to enabling -Wimplicit-fallthrough, mark switch cases where we are expecting to fall through. This patch fixes the following warning: In file included from drivers/scsi/dmx3191d.c:48: drivers/scsi/NCR5380.c: In function ‘NCR5380_information_transfer’: drivers/scsi/NCR5380.c:1933:9: warning: this statement may fall through [-Wimplicit-fallthrough=] if (!hostdata->connected) ^ drivers/scsi/NCR5380.c:1937:5: note: here default: ^~~~~~~ Warning level 3 was used: -Wimplicit-fallthrough=3 Notice that, in this particular case, the code comment is modified in accordance with what GCC is expecting to find. This patch is part of the ongoing efforts to enable -Wimplicit-fallthrough. Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> --- Changes in v2: - Update commit log. - Move code comment after the default label and retain reason for fall-through in comment as requested by Michael Schmitz. drivers/scsi/NCR5380.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)