>
>
>
> I believe that won't work with OCaml's GC because it contains a copying
> collector, obviating a total ordering over pairs of pointers.


The pointer used in total ordering is points outside the heap, into the
OCaml code (either machine code or byte-code), which, as far as I know, is
neither moved nor collected (although this would actually be a useful
feature, unloading modules...)