[cfe-commits] r75314 - in /cfe/trunk: include/clang/AST/ include/clang/Analysis/PathSensitive/ lib/AST/ lib/Analysis/ lib/CodeGen/ lib/Frontend/ lib/Sema/ test/CodeGenObjC/ test/PCH/ test/SemaObjC/ test/SemaObjCXX/

[steve naroff]

On Jul 13, 2009, at 4:58 PM, Fariborz Jahanian wrote:

>
> On Jul 13, 2009, at 1:18 PM, Chris Lattner wrote:
>
>>>
>>> Sure. How about isObjCBuiltinType() and isObjCBuiltinInterface()?
>
> IsObjCIdBuiltinType() and isObjCClassBuiltinType(). Somehow, names  
> should convey what they are.
>

Chris was suggesting we have a predicate to test for both 'id' and  
'Class'...

>>>
>>> GCC warns...
>>>
>>> test/SemaObjC/comptypes-5.m:29: warning: assignment from distinct  
>>> Objective-C type
>>> test/SemaObjC/comptypes-5.m:30: warning: assignment from distinct  
>>> Objective-C type
>>>
>>> I decided to allow it. Rationale: Both MyClass and MyOtherClass  
>>> implement MyProtocol. Since the protocols "match", and you can  
>>> assign any 'id' to an interface type (without warning), I decided  
>>> to allow it. I'm happy to put back the warning if others feel  
>>> strongly (Fariborz?).
>>
>> I'll let Fariborz make this call.
>
> We should probably put the warning back.  Lack of a warning looks  
> like a clang bug.  For example, clang (and gcc)
> both issue warning here:
>
> @protocol MyProtocol
> @end
>
> @interface MyClass
> @end
>
> int main()
> {
>  id <MyProtocol> obj_id_p;
>  MyClass *obj_c_cat_p;
>
>  obj_c_cat_p = obj_id_p;
>  return 0;
> }
>
> % $CLANGCC good.m
> good.m:12:15: warning: incompatible type assigning 'id<MyProtocol>',  
> expected 'MyClass *'
>  obj_c_cat_p = obj_id_p;
>
> But if you add a category conforming to the protocol (as in the  
> test), then warning disappears in clang. Categories do not
> enhance or change the type so behavior should not change.
>

Formally, I see your point (i.e. categories don't actually modify the  
type). Nevertheless, categories allow methods to be added to a class  
(a semantic that the compiler is very aware of). Since both categories  
and protocols are nothing more than "method containers", it seems like  
the compiler should be silent it determines the message can be sent.  
With dynamic typing and forwarding, all of this is speculative  
anyway:-) Just to be clear...I don't feel very strongly about this. I  
just think we should do what makes sense (and is in the spirit of the  
language). In this instance, I don't think GCC compatibility is a big  
issue...

My 2$,

snaroff

> - Fariborz
>
>
>
>
>>
>