| Message ID | 51A6EBC5.7040601@asianux.com |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
It seems a good idea to "fgrep -rn '~0U'" all source code, and check each one by one. :-) On 05/30/2013 02:03 PM, Chen Gang wrote: > > Both 'transport_header' and 'mac_header' are u16, which are never equal > to '~0U'. > > So need use '0xffff' instead of '~0U'. > > The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig) > include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits] > ... > > > Signed-off-by: Chen Gang <gang.chen@asianux.com> > --- > include/linux/skbuff.h | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 2e0ced1..03ba058 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb, > } > static inline bool skb_transport_header_was_set(const struct sk_buff *skb) > { > - return skb->transport_header != ~0U; > + return skb->transport_header != 0xffff; > } > > static inline unsigned char *skb_transport_header(const struct sk_buff *skb) > @@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb) > > static inline int skb_mac_header_was_set(const struct sk_buff *skb) > { > - return skb->mac_header != ~0U; > + return skb->mac_header != 0xffff; > } > > static inline void skb_reset_mac_header(struct sk_buff *skb) >
On Thu, 2013-05-30 at 14:03 +0800, Chen Gang wrote: > Both 'transport_header' and 'mac_header' are u16, which are never equal > to '~0U'. > > So need use '0xffff' instead of '~0U'. ...and give this magic number a name? Ben. > The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig) > include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits] > ... > > > Signed-off-by: Chen Gang <gang.chen@asianux.com> > --- > include/linux/skbuff.h | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 2e0ced1..03ba058 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb, > } > static inline bool skb_transport_header_was_set(const struct sk_buff *skb) > { > - return skb->transport_header != ~0U; > + return skb->transport_header != 0xffff; > } > > static inline unsigned char *skb_transport_header(const struct sk_buff *skb) > @@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb) > > static inline int skb_mac_header_was_set(const struct sk_buff *skb) > { > - return skb->mac_header != ~0U; > + return skb->mac_header != 0xffff; > } > > static inline void skb_reset_mac_header(struct sk_buff *skb)
On Thu, May 30, 2013 at 9:03 AM, Chen Gang <gang.chen@asianux.com> wrote: > > Both 'transport_header' and 'mac_header' are u16, which are never equal > to '~0U'. > > So need use '0xffff' instead of '~0U'. Why not "(u16)~0" ? Or even better "!= USHORT_MAX"? Or mac_header + 1 == 0, though it less clear. -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/30/2013 11:30 PM, Ben Hutchings wrote: > On Thu, 2013-05-30 at 14:03 +0800, Chen Gang wrote: >> > Both 'transport_header' and 'mac_header' are u16, which are never equal >> > to '~0U'. >> > >> > So need use '0xffff' instead of '~0U'. > ..and give this magic number a name? It sounds a good idea. I will check which name is suitable for it, then send patch v2, and please help to check it, too. Thanks.
On 06/01/2013 05:05 AM, Andy Shevchenko wrote: > On Thu, May 30, 2013 at 9:03 AM, Chen Gang <gang.chen@asianux.com> wrote: >> > >> > Both 'transport_header' and 'mac_header' are u16, which are never equal >> > to '~0U'. >> > >> > So need use '0xffff' instead of '~0U'. > Why not "(u16)~0" ? > Or even better "!= USHORT_MAX"? > > Or mac_header + 1 == 0, though it less clear. It seems they are just the same as '0xffff' (are all 'magic' number). We'd better to give a meaningful name to it just like Ben said. Thanks.
On Mon, Jun 3, 2013 at 12:23 PM, Chen Gang <gang.chen@asianux.com> wrote: > On 06/01/2013 05:05 AM, Andy Shevchenko wrote: >> Why not "(u16)~0" ? > We'd better to give a meaningful name to it just like Ben said. Yeah, you could give a name, though I don't see this needs for constants like (u16)~0. It's a usual way to mark some values uninitialized. Just an example from kernel: /* This is limited by 16 bit "slot" numbers, * and by available on-disk context storage. * * Also (u16)~0 is special (denotes a "free" extent). -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 06/03/2013 06:14 PM, Andy Shevchenko wrote: > On Mon, Jun 3, 2013 at 12:23 PM, Chen Gang <gang.chen@asianux.com> wrote: >> On 06/01/2013 05:05 AM, Andy Shevchenko wrote: > >>> Why not "(u16)~0" ? >> We'd better to give a meaningful name to it just like Ben said. > > Yeah, you could give a name, though I don't see this needs for > constants like (u16)~0. It's a usual way to mark some values > uninitialized. > Just an example from kernel: > > /* This is limited by 16 bit "slot" numbers, > * and by available on-disk context storage. > * > * Also (u16)~0 is special (denotes a "free" extent). > After "fgrep -rn 'u16' * | fgrep '~0'", it seems better to define a meaningful macro for it (e.g. "#define SKB_HEADER_WAS_UNSET 0xffff"). Thanks.
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 2e0ced1..03ba058 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb, } static inline bool skb_transport_header_was_set(const struct sk_buff *skb) { - return skb->transport_header != ~0U; + return skb->transport_header != 0xffff; } static inline unsigned char *skb_transport_header(const struct sk_buff *skb) @@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb) static inline int skb_mac_header_was_set(const struct sk_buff *skb) { - return skb->mac_header != ~0U; + return skb->mac_header != 0xffff; } static inline void skb_reset_mac_header(struct sk_buff *skb)
Both 'transport_header' and 'mac_header' are u16, which are never equal to '~0U'. So need use '0xffff' instead of '~0U'. The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig) include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits] ... Signed-off-by: Chen Gang <gang.chen@asianux.com> --- include/linux/skbuff.h | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)