During a call to compile-file, *compile-file-pathname* is bound to the pathname denoted by the first argument to compile-file, merged against the defaults; that is, it is bound to
(pathname (merge-pathnames input-file)). During the same time interval, *compile-file-truename* is bound to the truename of the file being compiled.
If a break loop is entered while compile-file is ongoing, it is implementation-dependent whether these variables retain the values they had just prior to entering the break loop or whether they are bound to nil.
The file system.