[cfe-dev] Fix for PR4701

[David Chisnall]

On 15 Aug 2009, at 02:37, Daniel Dunbar wrote:

> On Fri, Aug 14, 2009 at 6:30 PM, David  
> Chisnall<csdavec at swansea.ac.uk> wrote:
>> I'd like to keep it.  Long-term, I agree with Steve - having explicit
>> typedefs for what should be builtin types is an ugly hack.  If we  
>> leave it
>> in then users can slowly drop the includes of the headers that  
>> define these
>> types and fall back to using the compiler-supplied definitions.  In  
>> a little
>> while we can add a warning for files that define these types.
>
> To clarify, so your position is that long term clients should drop
> uses of the other fields, but direct assignment / reading of isa is
> ok?

Yes.  The Apple runtime.h already marks the fields other than isa as  
deprecated with the legacy runtime and unavailable on the modern  
runtime.

> One downside of that approach (aside from being speculative) is that
> it encourages users to write non-portable (to gcc) code. Since it is
> also speculative it seems to me to unnecessarily complicate clients,
> but I'm happy to defer to others opinions on this.

Not really a problem for the GNU runtime - any code that uses  
properties or fast enumeration will compile with clang but not GCC  
already because no one seems to be working on Objective-C in the FSF's  
tree and the Apple tree doesn't support the GNU runtime.  People using  
the Apple runtime almost always get these definitions via Foundation.h  
(often indirectly via Cocoa.h), so there's little chance of them  
accidentally writing code that doesn't include them (although a future  
version of the Apple headers may choose to wrap their definitions in  
#ifndef __clang__).

David