> -----Original Message----- > From: Yigit, Ferruh > Sent: Monday, November 5, 2018 10:31 PM > To: Zhao1, Wei <[email protected]>; Wu, Jingjing > <[email protected]>; Lu, Wenzhuo <[email protected]> > Cc: [email protected]; [email protected] > Subject: Re: [dpdk-dev] [PATCH] net/avf/base: fix shifting 32 bits signed > variable 31 times > > On 10/31/2018 3:34 AM, Zhao1, Wei wrote: > > > > > >> -----Original Message----- > >> From: dev [mailto:[email protected]] On Behalf Of Ferruh Yigit > >> Sent: Sunday, October 28, 2018 11:52 AM > >> To: Wu, Jingjing <[email protected]>; Lu, Wenzhuo > >> <[email protected]> > >> Cc: [email protected]; Yigit, Ferruh <[email protected]>; > >> [email protected] > >> Subject: [dpdk-dev] [PATCH] net/avf/base: fix shifting 32 bits signed > >> variable > >> 31 times > >> > >> Fixes: e5b2a9e957e7 ("net/avf/base: add base code for avf PMD") > >> Cc: [email protected] > >> > >> Signed-off-by: Ferruh Yigit <[email protected]> > >> --- > >> drivers/net/avf/base/avf_register.h | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/net/avf/base/avf_register.h > >> b/drivers/net/avf/base/avf_register.h > >> index ba5a9f3fa..adb989583 100644 > >> --- a/drivers/net/avf/base/avf_register.h > >> +++ b/drivers/net/avf/base/avf_register.h > >> @@ -76,7 +76,7 @@ POSSIBILITY OF SUCH DAMAGE. > >> #define AVF_ARQLEN1_ARQCRIT_SHIFT 30 > >> #define AVF_ARQLEN1_ARQCRIT_MASK AVF_MASK(0x1, > >> AVF_ARQLEN1_ARQCRIT_SHIFT) > >> #define AVF_ARQLEN1_ARQENABLE_SHIFT 31 -#define > >> AVF_ARQLEN1_ARQENABLE_MASK AVF_MASK(0x1, > >> AVF_ARQLEN1_ARQENABLE_SHIFT) > >> +#define AVF_ARQLEN1_ARQENABLE_MASK AVF_MASK(0x1U, > >> +AVF_ARQLEN1_ARQENABLE_SHIFT) > >> #define AVF_ARQT1 0x00007000 /* Reset: EMPR */ > >> #define AVF_ARQT1_ARQT_SHIFT 0 > >> #define AVF_ARQT1_ARQT_MASK AVF_MASK(0x3FF, > >> AVF_ARQT1_ARQT_SHIFT) @@ -99,7 +99,7 @@ POSSIBILITY OF SUCH > DAMAGE. > >> #define AVF_ATQLEN1_ATQCRIT_SHIFT 30 > >> #define AVF_ATQLEN1_ATQCRIT_MASK AVF_MASK(0x1, > >> AVF_ATQLEN1_ATQCRIT_SHIFT) > >> #define AVF_ATQLEN1_ATQENABLE_SHIFT 31 -#define > >> AVF_ATQLEN1_ATQENABLE_MASK AVF_MASK(0x1, > >> AVF_ATQLEN1_ATQENABLE_SHIFT) > >> +#define AVF_ATQLEN1_ATQENABLE_MASK AVF_MASK(0x1U, > >> +AVF_ATQLEN1_ATQENABLE_SHIFT) > >> #define AVF_ATQT1 0x00008400 /* Reset: EMPR */ > >> #define AVF_ATQT1_ATQT_SHIFT 0 > >> #define AVF_ATQT1_ATQT_MASK AVF_MASK(0x3FF, > >> AVF_ATQT1_ATQT_SHIFT) > >> -- > >> 2.17.2 > > > > I have test this code change with a small function to observe the > > difference. > > Reviewed-by: Wei Zhao <[email protected]> > > > > #define AVF_ARQLEN1_ARQENABLE_SHIFT 31 #define AVF_MASK(mask, > shift) > > (mask << shift) #define AVF_ARQLEN1_ARQENABLE_MASK1 > AVF_MASK(0x1, > > AVF_ARQLEN1_ARQENABLE_SHIFT) #define > AVF_ARQLEN1_ARQENABLE_MASK2 > > AVF_MASK(0x1U, AVF_ARQLEN1_ARQENABLE_SHIFT) > > > > void main(int argc,char **argv) > > { > > signed int a=1; > > > > printf("Hello Linux\n"); > > > printf("%x,=%x\n",AVF_ARQLEN1_ARQENABLE_MASK1,AVF_ARQLEN1_ARQ > ENABLE_MASK2); > > printf("a=%x\n",a<<31); > > > > } > > I guess you are tying to say there is no difference, output of your code is: > Hello Linux > 80000000,=80000000 > a=80000000 > > > Let's have a little addition to your program, #include <stdio.h> > > #define AVF_ARQLEN1_ARQENABLE_SHIFT 31 > #define AVF_MASK(mask, shift) (mask << shift) #define > AVF_ARQLEN1_ARQENABLE_MASK1 AVF_MASK(0x1, > AVF_ARQLEN1_ARQENABLE_SHIFT) #define > AVF_ARQLEN1_ARQENABLE_MASK2 AVF_MASK(0x1U, > AVF_ARQLEN1_ARQENABLE_SHIFT) #define AVF_MASK2(mask, shift) > (mask >> shift) #define AVF_ARQLEN1_ARQENABLE_MASK11 > AVF_MASK2(AVF_ARQLEN1_ARQENABLE_MASK1, 30) #define > AVF_ARQLEN1_ARQENABLE_MASK22 > AVF_MASK2(AVF_ARQLEN1_ARQENABLE_MASK2, 30) > > void main(int argc,char **argv) > { > signed int a=1; > > printf("Hello Linux\n"); > printf("%x,=%x\n", AVF_ARQLEN1_ARQENABLE_MASK1, > AVF_ARQLEN1_ARQENABLE_MASK2); > printf("%x,=%x\n", AVF_ARQLEN1_ARQENABLE_MASK11, > AVF_ARQLEN1_ARQENABLE_MASK22); > printf("a=%x\n", a<<31); > > } > > > Will results same for second line? Both does ((1 << 31) >> 30). > > > '1' is promoted to signed int by default and cppcheck complains that shifting > signed variable 31 times is undefined behaviour, and here intention is not > really have the 1 as signed integer, so better to fix it. >
Acked-by: Wei Zhao <[email protected]> > Thanks, > ferruh
