>> IMHO, each header item can be placed into the separate DATA section, so
>> it's not the real problem (the frame table is).
>
> No it can not. The moduler header must be contiguous and not rearranged by
> linker. In absence of .cmx (and name -> mangled name table) OCaml uses the
> header to call functions by position. Thus, as it is now, no part of
> header can be eliminated, which in reality means that almost everything,
> from linkers perspective, is reachable and can not be removed by 
> --gc-functions.

The module header oculd be generated by the linker, omitting
references to unused functions (filling the place with a null pointer
or something like that).