Re: [PATCH dwarves v9 2/3] pahole: Add --btf_feature=decl_tag_kfuncs feature

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Thu, May 02, 2024 at 12:49:26PM +0100, Alan Maguire wrote:
> On 01/05/2024 00:00, Daniel Xu wrote:
> > On Tue, Apr 30, 2024 at 03:48:06PM GMT, Arnaldo Carvalho de Melo wrote:
> >> On Mon, Apr 29, 2024 at 04:45:59PM -0600, Daniel Xu wrote:
> >> Also 'decl_tag_kfuncs' is not enabled when using --btf_features=default,
> >> right? as:

> >>         BTF_DEFAULT_FEATURE(decl_tag_kfuncs, btf_decl_tag_kfuncs, false),

> >> And that false is .default_enabled=false.

> > I think that `false` is for `initial_value`, isn't it? The macro sets
> > the `default_enabled` field.
 
> yep it's the initial unset value. Specifying an option in --btf_features
> flips that value, so for initial-off values they are switched on, while

So --btf_features=something may mean "don't use that feature"? That is
confusing, perhaps the '-something' come in handy?

> initial-on values are switched off. I _think_ the intent here is to tag
> kfuncs by default, so we can add tag_kfuncs to the set of options

Probably, if they are present in the file being BTF encoded.

> specified in pahole-flags for v1.26. We won't be using "default" there
> as we want to call out the flags explicitly.

Sure.

- Arnaldo