The GHC user manual includes this description of Addr# literals:

> `"foo"#` has type `Addr#`

That's the extent of the documentation. It should be mentioned that text is encoded with Modified UTF-8. Also, I am not even sure what happens to a string like "hello\x00world"#. Is it treated any differently than "hello\NULworld"#. I haven't checked, but the manual should document what byte sequences these correspond to.