Re: [MacOSX] gcc3.1-1145 for downloading

[Scott Christley]

On Tuesday, July 2, 2002, at 03:28 PM, address@hidden wrote:


> I am very much trying to work
> towards a version of Swarm which will compile and run on a MacOS X 
> system
> with the minimum modification.   Nirvana would be to end up with a Swarm
> framework which can be installed and then used to build apps in Project
> Builder using it, the AppKit framework and not much else.

If only it would be this easy, but unfortunately it will not.  Despite 
the fact that objc is the same, the different objc runtimes cannot 
intermix so easily.  It is more than just a linking issue; the actual 
compiled code is explicitly tied to the specific objc runtime.

When you compile objc code, every time the compiler sees a method call, 
it translates it into a bit a code that looks somewhat like this:

// 1. Have the objc runtime lookup the method.
// 2. Prepare the registers/stack with the method arguments.
// 3. Call the method
// 4. Clean up the stack and retrieve the return argument.

It looks all fine but operation #1 calls objc_msgSend() for the Apple 
runtime and objc_msg_lookup() for the GNU runtime.  GCC has two flags; 
-fgnu-runtime and -fnext-runtime which generates code for one or the 
other.  With the current gcc architecture, this flag operates on a file 
by file basis, so it is not possible to intermix calls with the two 
runtimes in the same file.  This was why I was trying to get Swarm to 
work with the Apple runtime, to avoid having to deal with this dual 
runtime system.

If we do get it to work, I suspect that there will need to be a proxy 
connection between the two runtimes, probably written in C.  In some 
ways, the Apple runtime has to be considered similar to how Java 
interacts with Swarm.  Swarm code won't be able to directly utilize any 
of the Cocoa classes and Cocoa code won't be able to directly 
create/call Swarm code.  All Swarm classes, including your agent code, 
will need to be compiled with the GNU runtime; while all the Cocoa code 
is compiled with the Apple runtime.  yucko...

cheers
Scott


                 ==================================
  Swarm-Support is for discussion of the technical details of the day
  to day usage of Swarm.  For list administration needs (esp.
  [un]subscribing), please send a message to <address@hidden>
  with "help" in the body of the message.