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 <[email protected]>
---
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 */
+ 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",
--
2.21.0
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 <[email protected]>
> ---
> 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 <[email protected]>
>> ---
>> 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",
--
Martin K. Petersen Oracle Linux Engineering