cc -O2 -pipe -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  -lstdthreads -lcrypt
sys_resource/setpriority.c:16:18: error: use of undeclared identifier 'NZERO'
   16 |         if ( priority < NZERO - 1 )
      |                         ^
1 error generated.