Re: Quick syntax/compatibility question with libobjc2 and clang 3.4+

[David Chisnall]

On 29 Apr 2014, at 04:32, Tom Bruno <thomas.bruno@me.com> wrote:

> I'm currently using libobjc2 and clang 3.4.  I was researching how NSObject 
> is implemented just learning the ins and outs (I'm very interested in the 
> memory management and such).
> 
> One of the things I've noticed is that placing variables in @implementation 
> does not work on linux but seems to work fine on osx like this (Sources at 
> end of email):
> 
> #import <objc/runtime.h>
> 
> @implementation MAObject {
>     Class isa;
>     volatile int32_t retainCount;
> }
> 
> 
> The compiler complains isa and retainCount do not exist.  I've kindof put 
> together that only OSX 64bit mode will work with this code.  Is this a 
> limitation in libobjc2 or clang on linux itself?  Is there something we can 
> do to support this new syntax?

This should work, however you will need to make sure that you are compiling for 
a modern ABI.  Do your OBJCFLAGS contain either -fobjc-nonfragile-abi, or 
(ideally) -fobjc-runtime=gnustep-1.7.

David




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