Re: [PATCH bpf-next 1/2] libbpf: add option to force-anonymize nested structs for BTF dump

[Eduard Zingerman <eddyz87@gmail.com>]

On Tue, 2025-12-16 at 17:18 +0000, Alan Maguire wrote:

[...]

> @@ -1460,10 +1466,16 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
>  		case BTF_KIND_UNION:
>  			btf_dump_emit_mods(d, decls);
>  			/* inline anonymous struct/union */
> -			if (t->name_off == 0 && !d->skip_anon_defs)
> +			if (t->name_off == 0 && !d->skip_anon_defs) {
>  				btf_dump_emit_struct_def(d, id, t, lvl);
> -			else
> +			} else if (decls->cnt == 0 && !fname[0] && d->force_anon_struct_members) {
> +				/* anonymize nested struct and emit it */
> +				btf_dump_set_anon_type(d, id, true);
> +				btf_dump_emit_struct_def(d, id, t, lvl);
> +				btf_dump_set_anon_type(d, id, false);


Hi Alan,

I think this is a solid idea.

It seems to me that with current implementation there would be a
trouble in the following scenario:

  struct foo { struct foo *ptr; };
  struct bar {
    struct foo;
  }

Because state for 'foo' will be anonymize == true at the moment when
'ptr' field is printed.

Maybe pass a direct parameter to btf_dump_emit_struct_def()?


> +			} else {
>  				btf_dump_emit_struct_fwd(d, id, t);
> +			}
>  			break;
>  		case BTF_KIND_ENUM:
>  		case BTF_KIND_ENUM64:

[...]