Am Montag, dem 07.04.2025 um 14:44 +0200 schrieb Michael Matz: > Hello, > > On Sat, 5 Apr 2025, Bill Wendling wrote: > > > > > > > So, a different attribute name “counted_by_exp” might be better? > > > > > > > > > > I would prefer Martins empty-decl idea to that: "counted_by(;len+0)" > > > > > (looks up 'len' normally, i.e. doesn't look into current struct). It > > > > > would naturally fit the either decl+expr or lone-ident parse. > > > > > It may look weird but empty declarations are okayish IMHO. > > > > > > > > > > But overall: I just don't know, it all looks a bit unsexy, there only > > > seem > > > > > to be rocks and hard places :) > > > > > > > > I would not worry about this case too much, because I do expect this > > > > to be a common use case anyway. That it looks strange may even be > > > > an advantage here, as it alerts the reader that this is unusual. > > > > > > This is an interesting point and also a good point. -:) > > > > > > The other thought that bother me a little bit is: > > > > > > For the same attribute, counted_by, is it strange to have two different > > > looking up rules > > > depending on the different number of arguments?l > > > > > > > Sorry for the HTML. On my phone. > > > > I think adding a ';' isn't the best option. It's too easy to overlook when > > reading the attribute and forget when writing the attribute. Using a > > separate attribute name is much cleaner, IMO. Then again, I've been wrong > > before. :-) > > So, what specifically would the two attributes do different? FWIW: what > worries me about accepting a generic expression in counted_by, that isn't > prefixed by a (possibly empty) decl, is that after seeing a non-type > identifier the parser doesn't yet know if it's the lone-ident case (look > up in struct scope) or the expression case (look up everything in global > scope). It requires look-ahead to decide this. > > Would that be the difference between the attributes? One accepting _only_ > a lone-ident or the decl+expr syntax, and the other _only_ expressions > that are never looked up in struct-scope (not even if its lone-ident)?
My understanding is that one accepts only a lone identifier and nothing else, i.e. counted_by(identifier) and the other only accepts expressions, possibly including a forward declaration. counted_by_expr(expression) counted_by_expr(decl; expression) And counted_by_expr(size_t id; id) would be equivalent to counted_by(id) when the struct has a member "id" with type size_t. Martin
