[cfe-dev] Objective-C runtime

[Fariborz Jahanian]

Some corrections below:

On Sep 17, 2010, at 4:00 PM, David Chisnall wrote:

> On 17 Sep 2010, at 23:29, Ariel V Feinerman wrote:
>
>> Can I use a custom runtime with the clang-llvm included in Xcode or  
>> vice versa Apple runtime in other OS with the clang-llvm (I wish to  
>> get full Objective C 2.0 support in win, linux or mac with the same  
>> lib) from llvm.org or source? In general, how do clang-llvm, llvm- 
>> gcc or gcc know what type of runtime you use? They may have some  
>> different interfaces.
>
> By default, clang will target the GNU runtime on non-Darwin  
> platforms and the NeXT / Apple runtimes when on on Darwin.  You can  
> control this in the same way that you do with GCC, by providing the - 
> fgnu-runtime or -fnext-runtime flag, to select between the GNU and  
> NeXT (Apple) runtimes explicitly.
>
> Providing -fobjc-nonfragile-abi will also make some changes to the  
> runtime.  On Darwin it will use Apple's 'Modern' runtime, while not  
> specifying it will generate code for the 'Legacy' runtime.  If you  
> specify -fobjc-nonfragile-abi and -fgnu-runtime, then clang will  
> generate code for the GNUstep runtime, which you can find in GNUstep  
> svn as libobjc2.  This provides all of the ObjC 2 features except  
> for GC, and a few others not found in the Mac runtimes.

On Darwin, default in clang's TOT is -fobjc-nonfragile-abi2 (the more  
modern runtime). Older releases of clang have -fobjc-nonfragile-abi by  
default.
To get legacy runtime, you can either add -m32 or -triple i386-apple- 
darwin9 on clang's command line.

- Fariborz


>
>
> Apple GCC never merged the code for supporting non-NeXT/Apple  
> runtimes, so Apple GCC (which is used by llvm-gcc) only supports the  
> NeXT / Apple runtimes.  Dragon Egg uses FSF GCC, so it will be able  
> to target the GNU and Apple runtimes.  FSF GCC does not currently  
> support Objective-C 2, but Nicola Pero is currently working on that.
>
> If you want to cross-compile from XCode, then you will need to do a  
> bit more than just select a different runtime (for example, make  
> sure you are including only headers for your target platform, and  
> probably using a non-Darwin version of binutils).
>
> David
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