PascalDragon, Thaddy, thanks! That makes things much more clear.
However, still, knowing which directives are defined on Linux is nice, but which directives would be defined on an Android phone or Mac desktop? I can't run fpc -vc or fpc -i there... Just trying to do cross-compilation.
(UPD) Hmm... a cross-compiler should display those correctly (as they're working compile-time, so I don't need to have FPC installed at the target)! I'll try it.