Re: [PATCH bpf] libbpf: fix deduplication of typedef with base definitions

[Antoine Tenart <atenart@kernel.org>]

On Thu, Apr 16, 2026 at 09:31:53AM +0100, Alan Maguire wrote:
> On 16/04/2026 08:38, Antoine Tenart wrote:
> > When deduplicating definitions for a module, typedef defined in the base
> > are not removed. This is because the hash used for base types differs
> > from the one used in the deduplication logic in btf_dedup_struct_type.
> > 
> > This was introduced by the referenced commit when moving the typedef
> > deduplication logic handling from btf_dedup_ref_type to
> > btf_dedup_struct_type, as this also changed the hash logic
> > (btf_hash_common to btf_hash_typedef).
> > 
> > This also impacts other types referencing those typedef (e.g. const). In
> > my test, the BTF section size of the openvswitch module went from 31KB
> > to 45KB.
> > 
> > Cc: Paul Houssel <paulhoussel2@gmail.com>
> > Fixes: 3781413465df ("libbpf: Fix BTF dedup to support recursive typedef definitions").
> > Signed-off-by: Antoine Tenart <atenart@kernel.org>
> 
> Nice catch! It would be great to have test coverage for this in
> prog_tests/btf_dedup_split.c ; adding a duplicated typedef to base and split
> BTF in test_split_simple() and ensuring it's removed from split BTF
> would do the trick I think.

Makes sense, I'll add a test for v2. Would you prefer a dedicated test
or reusing an existing one?