Re: [RFI]: getting objc to grok attributes ??

[Kaveh R. Ghazi]

 > From: Nicola Pero <address@hidden>


Nicola - Thanks for all of your comments/feedback!


 > [...]
 > The reason is that, while in C you define a function and normally the
 > function has a single implementation associated with it (so, if an
 > argument is unused, it's suspicious that there might be a mismatch between
 > the declaration and the implementation, and it's a good idea to warn), in
 > ObjC is very common to define a method in a place and have many different
 > implementations of the method in many different classes.  For example -

Yes, C++ (whose syntax I do know) is much the same.  In C++, one can
omit function/method parameter names when they are unused and g++
avoids warning in these cases.  E.g.

 > int foo (int a, int, char *)
 > { return a; }

Here g++ will not warn about the unused 2nd and 3rd arguments.  I
don't know objc syntax to suggest a similar mechanism.  (It may not be
possible, if you can omit the type there's no argument placeholder?)


 > Depending on the semantics of __attribute__ ((__unused__)) [does it mark
 > the argument as being possibly unused in that method implementation, or is
 > it a system-wide declaration that in all implementations of methods with
 > that name/signature the argument could be unused ?],

In frontends where its currently implemented, attributes on parameters
are specific to the exact function or method where one uses it.  I
would expect that if we extend objc to allow it we would follow this
convention.


 > So, maybe (from an ObjC user point of view) we should better disable the
 > warnings for unused method arguments, unless some -Wxxx option is included
 > to cause them (my bet is nobody will ever want to use that option, but
 > anyway).


If that's the consensus among objc developers fine, but I'm not sure I
like it and its beyond what I would be interested in implementing.
Its too blunt, I prefer a clean way of specifying which unused
identifiers are ignorable and warn about anything else.

Can you perhaps suggest something based on the C++ example I gave?

                --Kaveh
--
Kaveh R. Ghazi                  Director of Systems Architecture
address@hidden          Qwest Solutions