Before saying that, it would be interesting to know what
GetFullPathName() actually does. Does it `canonize'?
(realpath() does.) Does it resolve symbolic links. realpath()
does, and of course, Windows only has symbolic links since
Vista? (But what does GetFullPathName() do with short cuts?)
Note too that realpath() has a broken interface, which makes it
impossible to use in a correct program except in restricted
cases. At least, I was unable to find a way. Basically, it
requires that you provide a buffer of PATH_MAX bytes. but
PATH_MAX depends on the file system, and the file system depends
on the real path---you need the results of realpath() in order
to determine PATH_MAX. (I ended up re-implémenting it myself,
so that it would work robustly.)