Re: [PATCH bpf-next] tools/resolve_btfids: Warn when having multiple IDs for single type

On Tue, Jan 5, 2021 at 11:50 AM Jiri Olsa [off-list ref] wrote:

On Tue, Jan 05, 2021 at 11:37:09AM -0800, Alexei Starovoitov wrote:

quoted

On Tue, Jan 5, 2021 at 7:39 AM Jiri Olsa [off-list ref] wrote:

quoted

The kernel image can contain multiple types (structs/unions)
with the same name. This causes distinct type hierarchies in
BTF data and makes resolve_btfids fail with error like:

  BTFIDS  vmlinux
FAILED unresolved symbol udp6_sock

as reported by Qais Yousef [1].

This change adds warning when multiple types of the same name
are detected:

  BTFIDS  vmlinux
WARN: multiple IDs found for 'file' (526, 113351)
WARN: multiple IDs found for 'sk_buff' (2744, 113958)

We keep the lower ID for the given type instance and let the
build continue.

I think it would make sense to mention this decision in the warning.
'WARN: multiple IDs' is ambiguous and confusing when action is not specified.

ok, how about:

WARN: multiple IDs found for 'file': 526, 113351 - using 526

yep. much better imo.
Please add a comment to .c file with the suggestion that such types should
be renamed to avoid ambiguity.
Adding 'please rename' to WARN is probably overkill.