2021-11-05 17:19:06

by Anders Roxell

Subject: [PATCH] selftests: timers: use 'llabs()' over 'abs()'

When building selftests/timers with clang, the compiler warn about the
function abs() see below:

posix_timers.c:69:6: warning: absolute value function 'abs' given an argument of type 'long long' but has parameter of type 'int' which may cause truncation of value [-Wabsolute-value]
if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
^
posix_timers.c:69:6: note: use function 'llabs' instead
if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
^~~
llabs

The note indicates what to do, Rework to use the function 'llabs()'.

Signed-off-by: Anders Roxell <[email protected]>
---
tools/testing/selftests/timers/posix_timers.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
index 337424c5c987..73fb27901a1d 100644
--- a/tools/testing/selftests/timers/posix_timers.c
+++ b/tools/testing/selftests/timers/posix_timers.c
@@ -66,7 +66,7 @@ static int check_diff(struct timeval start, struct timeval end)
diff = end.tv_usec - start.tv_usec;
diff += (end.tv_sec - start.tv_sec) * USECS_PER_SEC;

- if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
+ if (llabs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
printf("Diff too high: %lld..", diff);
return -1;
}
--
2.33.0

2021-11-05 20:47:13

by Nick Desaulniers

Subject: Re: [PATCH] selftests: timers: use 'llabs()' over 'abs()'

On Fri, Nov 5, 2021 at 9:34 AM Anders Roxell <[email protected]> wrote:
>
> When building selftests/timers with clang, the compiler warn about the
> function abs() see below:
>
> posix_timers.c:69:6: warning: absolute value function 'abs' given an argument of type 'long long' but has parameter of type 'int' which may cause truncation of value [-Wabsolute-value]
> if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
> ^
> posix_timers.c:69:6: note: use function 'llabs' instead
> if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
> ^~~
> llabs
>
> The note indicates what to do, Rework to use the function 'llabs()'.
>
> Signed-off-by: Anders Roxell <[email protected]>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <[email protected]>

I wonder why tools/testing/selftests/timers/adjtick.c redefines llabs
when it already includes stdlib.h, and how that doesn't result in some
kind of compiler diagnostic.

> ---
> tools/testing/selftests/timers/posix_timers.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
> index 337424c5c987..73fb27901a1d 100644
> --- a/tools/testing/selftests/timers/posix_timers.c
> +++ b/tools/testing/selftests/timers/posix_timers.c
> @@ -66,7 +66,7 @@ static int check_diff(struct timeval start, struct timeval end)
> diff = end.tv_usec - start.tv_usec;
> diff += (end.tv_sec - start.tv_sec) * USECS_PER_SEC;
>
> - if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
> + if (llabs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
> printf("Diff too high: %lld..", diff);
> return -1;
> }
> --
> 2.33.0
>


--
Thanks,
~Nick Desaulniers

2021-11-20 00:07:33

by Shuah Khan

Subject: Re: [PATCH] selftests: timers: use 'llabs()' over 'abs()'

On 11/5/21 2:44 PM, Nick Desaulniers wrote:
> On Fri, Nov 5, 2021 at 9:34 AM Anders Roxell <[email protected]> wrote:
>>
>> When building selftests/timers with clang, the compiler warn about the
>> function abs() see below:
>>
>> posix_timers.c:69:6: warning: absolute value function 'abs' given an argument of type 'long long' but has parameter of type 'int' which may cause truncation of value [-Wabsolute-value]
>> if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
>> ^
>> posix_timers.c:69:6: note: use function 'llabs' instead
>> if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
>> ^~~
>> llabs
>>
>> The note indicates what to do, Rework to use the function 'llabs()'.
>>
>> Signed-off-by: Anders Roxell <[email protected]>
>
> Thanks for the patch!
> Reviewed-by: Nick Desaulniers <[email protected]>
>
> I wonder why tools/testing/selftests/timers/adjtick.c redefines llabs
> when it already includes stdlib.h, and how that doesn't result in some
> kind of compiler diagnostic.
>

Hmm. The define in /usr/include/stdlib.h is under #ifdef __USE_ISOC99
Maybe be that explains the reason for the definitions in the other two
timers file?

Anders, I would like to understand this before I take this patch. I see
you sent several patches to other tests as well. Would be useful at
least understand why these defines exist.

thanks,
-- Shuah