cc -pipe -O   -pthread  -Wall -Wextra -Werror=implicit-function-declaration sys_resource/setpriority.c -o sys_resource/setpriority -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread -lrt  -lrt -lcrypt
sys_resource/setpriority.c: In function 'main':
sys_resource/setpriority.c:16:18: error: 'NZERO' undeclared (first use in this function)
  if ( priority < NZERO - 1 )
                  ^~~~~
sys_resource/setpriority.c:16:18: note: each undeclared identifier is reported only once for each function it appears in