clang -O2  -Wall -Wextra -Werror=implicit-function-declaration fcntl/posix_fallocate.c -o fcntl/posix_fallocate -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
fcntl/posix_fallocate.c:16:16: error: implicit declaration of function 'posix_fallocate' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        if ( (errno = posix_fallocate(fileno(fp), 1, 2)) )
                      ^
1 error generated.