[missing-sync-palmos-dev-talk] Using Cocoa in a Carbon conduit

[Stuart A. Malone]

Joe, I think you may have been onto something when you wrote:

> Is there any need to bundle all the Cocoa functionality into a
> seperate bundle and load it lazily like that mentioned
> http://developer.apple.com/documentation/Cocoa/Conceptual/ 
> CarbonCocoaDoc/Articles/LazyCocoaLoading.html
> in order to let the conduit work under Palm Desktop?
>
> I ask because it says in the article, "You may want to use lazy
> initialization if the Cocoa functionality that you need is not always
> required by all users or your application uses CFM."

I believe that I have just run into this issue.  Palm Desktop crashes  
when it attempts to unload my mixed Carbon/Cocoa bundle under  
Panther.  I'm still researching the issue, but I wanted to mention it  
right away so that we can put our heads together and work out a  
solution.

The crash looks like this:

Thread 3 Crashed:
0   libobjc.A.dylib                	0x9086be80 _objc_trap + 0
1   libobjc.A.dylib                	0x9086be14 _objc_fatal + 0x48
2   libobjc.A.dylib                	0x90867c44 _objc_fatalHeader + 0x44
3   dyld                           	0x8fe182c0  
call_funcs_for_remove_image + 0x8c
4   dyld                           	0x8fe13220 _dyld_unlink_module +  
0xcc
5   libSystem.B.dylib              	0x9003db4c NSUnLinkModule + 0x68
6   com.apple.CoreFoundation       	0x90236290  
_CFBundleDYLDUnloadBundle + 0x3c
7   com.apple.CoreFoundation       	0x9021da00  
CFBundleUnloadExecutable + 0xe8
8   Conduit Manager                	0x0040dcc0 0x405000 + 0x8cc0

Some searching turned up a couple of interesting messages from  
Apple's mailing lists:

	http://lists.apple.com/archives/cocoa-dev/2001/Dec/msg00592.html

	http://lists.apple.com/archives/carbon-development/2003/Nov/ 
msg01760.html

The Cocoa documentation <http://developer.apple.com/documentation/ 
Cocoa/Conceptual/LoadingCode/LoadingCode.html> from 2003-01-13 says:

	Due to a limitation in the Objective-C runtime system, at the time
	of writing there is no way to unload Cocoa loadable bundles.

There is a similar warning at the bottom of <http:// 
developer.apple.com/documentation/Cocoa/Conceptual/LoadingCode/ 
Concepts/CFNSBundle.html>:

	Because of a limitation in the Objective-C runtime system, NSBundle
	cannot unload executable code. Since CFBundle does not know about
	Objective-C symbols, do not use the CFBundle loading and unloading
	routines on NSBundle objects. You can, however, create a CFBundle
	object for a Cocoa bundle and use the other routines—unrelated to
	loading and unloading—without trouble.

So I think the solution is probably to follow Apple's instructions  
for "Loading Cocoa Lazily Into Your Carbon Application":

	<http://developer.apple.com/documentation/Cocoa/Conceptual/ 
CarbonCocoaDoc/Articles/LazyCocoaLoading.html>

First, I'm going to see if I can isolate and eliminate our conduit's  
dependencies on Cocoa, but if that's not possible, I'll try following  
Apple's instructions for lazy loading.

I'll let you all know how it goes.  I'd also welcome thoughts on  
other solutions.


Best wishes,

--Stuart A. Malone
   Llamagraphics, Inc.
   Makers of Life Balance personal coaching software
   http://www.llamagraphics.com/