On 04/25/2013 11:40 AM, Chen Gang wrote:
> Need change ~(u8)0 to 0xff, or in mac802154_wpan_xmit(), "u8 chan"
> will never == MAC802154_CHAN_NONE.
>
> The related warning:
> net/mac802154/wpan.c:325:2: warning: comparison is always false
> due to limited range of data type [-Wtype-limits]
Hm, do you really need to include this huge pile of code below into the
commit message?
Couldn't you make the commit message simpler resp. more compact, e.g.:
Change MAC802154_CHAN_NONE from ~(u8)0 to 0xff, otherwise the comparison
in mac802154_wpan_xmit() for ``chan == MAC802154_CHAN_NONE'' will not succeed.
This bug can be boiled down to ``u8 foo = 0xff; if (foo == ~(u8)0) [...]
else [...]'' where the condition will always take the else branch.
.... something like that maybe?
> The related unit test:
> cc -Wall -O2 -o test test.c
> ./test
> will output 'different'
>
> (after use '0xff' instead of '~(u8)0', it will output 'equal')
>
> -----------------------test code begin--------------------------------
>
> #include <stdio.h>
>
> typedef unsigned char u8;
>
> int main()
> {
> u8 uc = 0xff;
>
> if (uc == ~(u8)0)
> printf("\nequal\n");
> else
> printf("\ndifferent\n");
>
> return 0;
> }
>
> -----------------------test code end----------------------------------
>
>
> Signed-off-by: Chen Gang <[email protected]>
> ---
> net/mac802154/mac802154.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/mac802154/mac802154.h b/net/mac802154/mac802154.h
> index a4dcaf1..703c121 100644
> --- a/net/mac802154/mac802154.h
> +++ b/net/mac802154/mac802154.h
> @@ -90,7 +90,7 @@ struct mac802154_sub_if_data {
>
> #define MAC802154_MAX_XMIT_ATTEMPTS 3
>
> -#define MAC802154_CHAN_NONE (~(u8)0) /* No channel is assigned */
> +#define MAC802154_CHAN_NONE 0xff /* No channel is assigned */
>
> extern struct ieee802154_reduced_mlme_ops mac802154_mlme_reduced;
> extern struct ieee802154_mlme_ops mac802154_mlme_wpan;
>
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