Em Thu, Oct 12, 2023 at 01:35:41PM +0100, Alan Maguire escreveu: > On 11/10/2023 23:14, Eduard Zingerman wrote: > > On Wed, 2023-10-11 at 23:05 +0100, Alan Maguire wrote: > > [...] > >>>>> I'm not sure I understand the logic behind "skip" features. > >>>>> Take `decl_tag` for example: > >>>>> - by default conf_load->skip_encoding_btf_decl_tag is 0; > >>>>> - if `--btf_features=decl_tag` is passed it is still 0 because of the > >>>>> `skip ? false : true` logic. > >>>>> > >>>>> If there is no way to change "skip" features why listing these at all? > >>>>> > >>>> You're right; in the case of a skip feature, I think we need the > >>>> following behaviour > >>>> > >>>> 1. we skip the encoding by default (so the equivalent of > >>>> --skip_encoding_btf_decl_tag, setting skip_encoding_btf_decl_tag > >>>> to true > >>>> > >>>> 2. if the user however specifies the logical inversion of the skip > >>>> feature in --btf_features (in this case "decl_tag" - or "all") > >>>> skip_encoding_btf_decl_tag is set to false. > >>>> > >>>> So in my code we had 2 above but not 1. If both were in place I think > >>>> we'd have the right set of behaviours. Does that sound right? > >>> > >>> You mean when --features=? is specified we default to > >>> conf_load->skip_encoding_btf_decl_tag = true, and set it to false only > >>> if "all" or "decl_tag" is listed in features, right? > >>> > >> > >> Yep. Here's the comment I was thinking of adding for the next version, > >> hopefully it clarifies this all a bit more than the original. > >> > >> +/* --btf_features=feature1[,feature2,..] allows us to specify > >> + * a list of requested BTF features or "all" to enable all features. > >> + * These are translated into the appropriate conf_load values via > >> + * struct btf_feature which specifies the associated conf_load > >> + * boolean field and whether its default (representing the feature being > >> + * off) is false or true. > >> + * > >> + * btf_features is for opting _into_ features so for a case like > >> + * conf_load->btf_gen_floats, the translation is simple; the presence > >> + * of the "float" feature in --btf_features sets conf_load->btf_gen_floats > >> + * to true. > >> + * > >> + * The more confusing case is for features that are enabled unless > >> + * skipping them is specified; for example > >> + * conf_load->skip_encoding_btf_type_tag. By default - to support > >> + * the opt-in model of only enabling features the user asks for - > >> + * conf_load->skip_encoding_btf_type_tag is set to true (meaning no > >> + * type_tags) and it is only set to false if --btf_features contains > >> + * the "type_tag" feature. > >> + * > >> + * So from the user perspective, all features specified via > >> + * --btf_features are enabled, and if a feature is not specified, > >> + * it is disabled. > >> */ > > > > Sounds reasonable. Maybe also add a line saying that > > skip_encoding_btf_decl_tag defaults to false if --btf_features is not > > specified to remain backwards compatible? > > > > good idea, will do! Thanks! I have to catch up with all the comments on this thread, but does this mean you're respinning the series now? - Arnaldo
