Q:

Error with expand-file-name function in emacs lisp

I'm using Emacs 25.2.1 under Arch Linux. 
When I try to expand /.. or /../ or /../rest/of/path paths with expand-file-name, there is not changes.  Is it a bug?  Could I use other (better) function? 
Thanks

A:

This is the intended behavior: /../ is the "super-root" on certain file systems:

Some Unix systems support a directory below the root directory.  Normally, "/.." points back to the same inode as "/", however, under MUNIX, this can be changed to point to a super-root directory, where remote trees can be mounted.  If, for example, two workstations "pcs2a" and "pcs2b" were connected via "connectnodes" and "uunite" startup script, "/../pcs2b" could be used to access the root directory of "pcs2b" from "pcs2a".