gcc -pthread -Wall -Wextra -Werror=implicit-function-declaration unistd/_Fork.c -o unistd/_Fork -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lxnet -lsocket -latomic unistd/_Fork.c: In function 'main': unistd/_Fork.c:9:21: error: implicit declaration of function '_Fork' [-Wimplicit-function-declaration] 9 | pid_t pid = _Fork(); | ^~~~~