cc -pipe -O   -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  -lrt -lcrypt
unistd/_Fork.c: In function 'main':
unistd/_Fork.c:9:14: error: implicit declaration of function '_Fork'; did you mean 'rfork'? [-Werror=implicit-function-declaration]
  pid_t pid = _Fork();
              ^~~~~
              rfork
cc1: some warnings being treated as errors