On 5/3/2024 9:52 AM, John Hubbard wrote:
On 5/3/24 1:00 AM, Ilpo Järvinen wrote:
On Thu, 2 May 2024, John Hubbard wrote:
...
diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c index d67ffa3ec63a..c873793d016d 100644 --- a/tools/testing/selftests/resctrl/mbm_test.c +++ b/tools/testing/selftests/resctrl/mbm_test.c @@ -33,7 +33,7 @@ show_bw_info(unsigned long *bw_imc, unsigned long *bw_resc, size_t span) avg_bw_imc = sum_bw_imc / 4; avg_bw_resc = sum_bw_resc / 4; - avg_diff = (float)labs(avg_bw_resc - avg_bw_imc) / avg_bw_imc; + avg_diff = (float)(avg_bw_resc - avg_bw_imc) / avg_bw_imc; avg_diff_per = (int)(avg_diff * 100); ret = avg_diff_per > MAX_DIFF_PERCENT;
But how are these two cases same after your change when you ended up removing taking the absolute value entirely?
All of the arguments are unsigned integers, so all arithmetic results are interpreted as unsigned, so taking the absolute value of that is always a no-op.
It does not seem as though clang can see when values have been casted. I tried to do so explicitly with a: avg_diff = labs((long)avg_bw_resc - avg_bw_imc) / (float)avg_bw_imc;
But that still triggers: warning: taking the absolute value of unsigned type 'unsigned long' has no effect [-Wabsolute-value]
Looks like we may need to be more explicit types and not rely on casting so much to make the compiler happy.
Reinette