cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations sched/sched_getscheduler.c -o sched/sched_getscheduler -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
sched/sched_getscheduler.c:6:21: error: use of undeclared identifier 'sched_getscheduler'
int (*foo)(pid_t) = sched_getscheduler;
                    ^
1 error generated.