Re: [Xen-devel] [PATCH 19/28] libxl: ocaml: add dominfo_list and dominfo_get

[Rob Hoes <Rob.Hoes@xxxxxxxxxx>]

[...]
> > +   domlist = temp = Val_emptylist;
> > +   for (i = nb - 1; i >= 0; i--) {
> > +           domlist = caml_alloc_small(2, Tag_cons);
> > +           Field(domlist, 0) = Val_int(0);
> > +           Field(domlist, 1) = temp;
> > +           temp = domlist;
> > +
> > +           Store_field(domlist, 0, Val_dominfo(&c_domlist[i]));
> 
> Is the preceding "Field(domlist, 0) = Val_int(0);" storing to the same place
> and therefore redundant?

I think the main reason to do this here is that caml_alloc_small (a low-level 
function) does not initialise the fields (as Dave pointed out earlier), and it 
is necessary to initialise the fields before doing any subsequent allocation on 
the OCaml heap (e.g. in Val_dominfo). If you don't do that, the GC may try to 
evaluate the uninitialised value.

Cheers,
Rob
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