$ rm -rf target/test/; mkdir target/test/; cp LICENSE "" README.md target/test/; echo "EXITCODE GNU: $?"; ls -l target/test/; echo "(end)"      
cp: cannot stat '': No such file or directory
EXITCODE GNU: 1
total 12
-rw-r--r-- 1 user user 1056 Apr  1 21:12 LICENSE
-rw-r--r-- 1 user user 7973 Apr  1 21:12 README.md
(end)
$ rm -rf target/test/; mkdir target/test/; cargo run cp LICENSE "" README.md target/test/; echo "EXITCODE uutils: $?"; ls -l target/test/; echo "(end)"
    Finished dev [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/coreutils cp LICENSE '' README.md target/test/`
error: a value is required for '[paths]...' but none was supplied

For more information, try '--help'.
EXITCODE uutils: 1
total 0
(end)