Perfect, Greg, thanks!!
On Nov 5, 2010, at 4:11 PM, Greg Parker wrote:
> On Nov 5, 2010, at 2:01 PM, Andy O'Meara wrote:
>> I'm having an issue with using objc_registerThreadWithCollector() under
>> earlier versions of OS X. 10.4 cancels my app load because it can't resolve
>> that symbol at dynamic link time, so I'm trying to figure out how to fetch
>> the symbol address by name. Of course, if the symbol isn't present then it
>> won't be called. I have to be able to build and ship a binary that works
>> under 10.4 so I can't just make the min OS version 10.6 at build time.
>>
>> Can you suggest or point me toward a snippet that demonstrates a
>> Cocoa-resident symbol lookup?
>
> It's supposed to work like this using weak symbol import:
>
> if (objc_registerThreadWithCollector) {
> objc_registerThreadWithCollector();
> } else {
> // do something else
> }
>
> but (1) objc_registerThreadWithCollector is missing the required availability
> declaration in the current SDKs, and (2) there's a compiler "optimization"
> that assumes the `if` condition is always true.
>
> The alternative is dynamic lookup like this:
>
> #include <dlfcn.h>
> void (*registerThreadWithCollector_fn)(void);
> registerThreadWithCollector_fn = (void(*)(void)) dlsym(RTLD_NEXT,
> "objc_registerThreadWithCollector");
> if (registerThreadWithCollector_fn) {
> (*registerThreadWithCollector_fn)();
> } else {
> // do something else
> }
>
> The lookup can be slow, so you should do it once and save the result.
>
>
> --
> Greg Parker [email protected] Runtime Wrangler
>
>
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