cc -pthread -Wall -Wextra -Werror=implicit-function-declaration unistd/nice.c -o unistd/nice -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lintl -liconv relibc getrlimit(3, 0x7ffffffffc80): not implemented relibc getrlimit(3, 0x7ffffffffba0): not implemented relibc getrlimit(9, 0x7ffffffffb60): not implemented relibc getrlimit(9, 0x7ffffffffb90): not implemented relibc getrlimit(5, 0x7ffffffffb90): not implemented relibc getrlimit(9, 0x7ffffffffb60): not implemented unistd/nice.c: In function 'main': unistd/nice.c:11:14: error: implicit declaration of function 'nice' [-Werror=implicit-function-declaration] 11 | if ( nice(0) < 0 && errno ) | ^~~~ cc1: some warnings being treated as errors