Lyberta:
> I'm thinking of abstraction where there is a virtual function call
> overhead but not a syscall overhead for every comparison and where there
> is still possible to compare paths to nonexistent files even when the
> actual comparison algorithm is implementation defined.

On the second thought, yes, a path component may be on exotic VFS that
can't be known ahead of time. So there is a way to optimize for common
cases like NTFS on Windows and EXT4 on Linux but no way to implement
general case without calling the OS to do actual comparison every time.