clang -O2  -Wall -Wextra -Werror=implicit-function-declaration unistd/fexecve.c -o unistd/fexecve -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
unistd/fexecve.c:30:2: error: implicit declaration of function 'fexecve' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        fexecve(fd, args, environ);
        ^
unistd/fexecve.c:30:2: note: did you mean 'execve'?
/usr/include/unistd.h:109:6: note: 'execve' declared here
int      execve(const char *, char * const *, char * const *);
         ^
1 error generated.