Re: Objective-C++

[Marcel Weiher]

On 27 Apr 2005, at 02:23, Greg Parker wrote:

> * fast dispatching
> The compiler assumes that a copy of objc_msgSend() is at a fixed  
> memory address, and jumps directly to it. This is most useful in  
> the context of PowerPC and Mac OS X's dynamic linker: the dynamic  
> linker overhead for cross-library calls is significant, and the  
> fast objc_msgSend() can be placed in a memory range that is  
> reachable by single absolute branch instruction. I don't know how  
> interesting this change is for GNUstep, given GNUstep's portability  
> goals.

Great!!   (Note:  almost half the cost of a message send on OS X was  
going through the cross-library call, so this is fantastic).  Would  
it be possible to have it go through a pointer instead, and have that  
pointer then take part in normal compiler optimizations?

> * GC
> Apple is working on a garbage collection system for Objective-C. It  
> is still under development, but does not use the Boehm GC available  
> in GNUstep. These compiler changes mostly add a write barrier when  
> assigning Objective-C instance pointers to ivars and a few other  
> places. The write barrier is a runtime function, and is similar to  
> the fast dispatching above. This is likely to evolve further, and  
> probably isn't interesting for GNUstep yet.

Interesting, especially the idea of a more indirect variable access  
mechanism.

Great news, overall.

Cheers,

Marcel