cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration spawn/posix_spawnattr_setschedpolicy.c -o spawn/posix_spawnattr_setschedpolicy -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
spawn/posix_spawnattr_setschedpolicy.c:28:17: error: call to undeclared function 'sched_getscheduler'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   28 |         if ( (policy = sched_getscheduler(0)) < 0 &&
      |                        ^
spawn/posix_spawnattr_setschedpolicy.c:34:48: error: use of undeclared identifier 'POSIX_SPAWN_SETSCHEDULER'
   34 |         if ( (errno = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSCHEDULER)) )
      |                                                       ^
spawn/posix_spawnattr_setschedpolicy.c:36:16: error: call to undeclared function 'posix_spawnattr_setschedpolicy'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   36 |         if ( (errno = posix_spawnattr_setschedpolicy(&attr, policy)) )
      |                       ^
3 errors generated.