Add rules for ObjC files

[Stan Shebs]

Klee Dienes wrote:

> I'm not sure if this is something you want to hassle with at the  
> moment, or if you'd prefer to let it wait as a modification once a  
> working version of the Objective-C patches are successfully committed.
>
> But just as a heads-up, I should mention that in more recent versions  
> of our GDB, we've folded in all of the Objective-C support directly  
> into c-exp.y, and removed objc-exp.y as a file entirely.  Most of  
> objc-exp.y was always just an out-of-date copy of c-exp.y, anyway;  
> moving the (rather small) changes into c-exp.y directly not only  
> allowed us to track changes to the C parser much more smoothly, it  
> should also allow for much better Objective-C++ support.
>
> You'll probably want to look at the most recent version of our GDB 
> tree  
> (http://www.opensource.apple.com/projects/darwin/6.0/source/other/gdb- 
> 20020918.tar.gz; no registration or anything similar required), and  
> check out our changes to c-exp.y; I've attached them for your  
> convenience.
>
> One downside to having the changes directly in c-exp.y is that I don't 
> know of any good way to conditionalize them; though I am by no means a 
> bison guru.

ObjC is supposed to be a strict superset of C, so at least in theory,
extensions don't need to be conditionalized at all, or they can be
disallowed after parsing, if you wanted to have a "strict C mode"
(although I note that the little array@45 extension is always available,
even though it's not valid C).

Stan