GC-optional mode: does anyone care?

[David Chisnall]

Hi Everyone,

On OS X, you can compile in one of three modes with respect to garbage 
collection:

1 No GC, normal retain/release semantics.
2GC-only, no retain/release stuff is used anywhere.
3 Optional GC, uses GC mode if everything that is linked supports GC, otherwise 
uses normal retain/release semantics.

GNUstep has supported the first mode forever.  I now have the second mode 
working quite nicely - still needs more testing, but Gorm and all of the Étoilé 
code that I've tried seems to work.

So, my question is whether it's worth supporting the GC-optional mode.  Code 
compiled in this mode will still send retain / release messages, but they'll be 
ignored if you're in GC mode.  The compiler will always insert the read and 
write barriers, but the runtime will ignore them if you're not in GC mode.  

This will require some tweaking in GNUstep code (things that are currently 
compile-time options will have to be modified to be switched at run time, for 
example we need both versions of the autorelease pool code.  On OS X, the main 
advantage is that you can ship binary-only frameworks that work in both modes 
(albeit with some performance overhead).  I'm not really sure that this is 
interesting to us, so before I waste time on a feature that no one will use, I 
thought I'd ask if anyone cares.  

David

-- Sent from my PDP-11