cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration time/clock_getcpuclockid.c -o time/clock_getcpuclockid -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
time/clock_getcpuclockid.c:12:15: error: call to undeclared function 'clock_getcpuclockid'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   12 |         int errnum = clock_getcpuclockid(getpid(), &id);
      |                      ^
1 error generated.