Pavel Pisa commented on a discussion on cpukit/dev/can/can-bittiming.c: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/726#note_132780 > sample_point = 1000 * ( tseg + CAN_CALC_SYNC_SEG - tseg2 ) / > ( tseg + CAN_CALC_SYNC_SEG ); > > - sample_point_error = abs( sample_point_nominal - sample_point ); > + sample_point_error = sample_point_nominal - sample_point; The removing of the abs would lead to disaster. The result would be finding combination of parameters with maximal negative error. The next test program works correctly ``` #include <stdio.h> #include <stdlib.h> volatile unsigned int a = 10; volatile unsigned int b = 11; volatile unsigned int c; int main(void) { int d = a - b; c = abs(a - b); printf("%d = %d - %d, abs = %u\n",d, a, b, c); return 0; } ``` Output ``` -1 = 10 - 11, abs = 1 ``` So the `-1` is correctly changed to the `+1`. This effect is necessary to count absolute error. But you are right that compiling even with mine GCC and `-Wabsolute-value` ``` gcc (Debian 12.2.0-14+deb12u1) 12.2.0 ``` ends by ``` gcc -Wall -Wabsolute-value t4.c && ./a.out t4.c: In function ‘main’: t4.c:11:7: warning: taking the absolute value of unsigned type ‘unsigned int’ has no effect [-Wabsolute-value] 11 | c = abs(a - b); | ^~~ ``` But output is correct ``` -1 = 10 - 11, abs = 1 ``` Test by ``` gcc (Debian 14.2.0-19) 14.2.0 ``` gives same warning but the result is the same. -- View it on GitLab: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/726#note_132780 You're receiving this email because of your account on gitlab.rtems.org.
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