On Fri, Apr 23, 2021 at 9:31 AM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
> > >
> > > static int remap_type_id(__u32 *type_id, void *ctx)
> > > {
> > > int *id_map = ctx;
> > > int new_id = id_map[*type_id];
> > >
> > >
> > > /* Here VOID stays VOID, that's all */
> > >
> > > if (*type_id == 0)
> > > return 0;
> >
> > Does it mean that id_map[0] is a garbage value?
> > and all other code that might be doing id_map[idx] might be reading
> > garbage if it doesn't have a check for idx == 0 ?
>
> No, id_map[0] == 0 by construction (id_map is obj->btf_type_map and is
> calloc()'ed) and can be used as id_map[idx].
Ok. Then why are you insisting on this micro optimization to return 0
directly?
That's the confusing part for me.
If it was:
"if (new_id == 0 && *type_id != 0) { pr_warn"
Then it would be clear what error condition is about.
But 'return 0' messing things up in my mind,
because it's far from obvious that first check is really a combination
with the 2nd check and by itself it's a micro optimization to avoid
reading id_map[0].
