ld: duplicate symbol _objc_retainedObject on iOS 4.3 , but not on iOS 5.0

Question

Some background - I've built a custom Framework using Diney's guide at http://db-in.com/blog/2011/07/universal-framework-iphone-ios-2-0/

Its built for both armv6 / armv7 , its an ARC-based framework, compiled with a depolyment target of 4.3.

When i put the resulting framework in a 5.0 project it works great, but when i put it in a 4.3 project (ARC or non-arc, doesnt matter), i get the following which i can't really understand ...

I've also tried adding libarclite.a manually but it didn't change anything.

ld: duplicate symbol _objc_retainedObject in /Users/freak4pc/Project/MyFramework.framework/MyFramework and /Developer/Platforms/iPhoneOS.platform/Developer/usr/lib/arc/libarclite_iphoneos.a(arclite.o) for architecture armv7 Command /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/clang failed with exit code 1

Would appreciate any help on this.
Thanks
Shai

Answer 1

I'm struggling with the same problem. The workaround is so set the deployment target of your framework to iOS5 (check if that doesn't make other problems though).

Then you must use ARC in the master project if targeting iOS4, else libarclite will be missing. My solution will be to supply two frameworks, depending if they use ARC or not.

Here's two links to Apple's dev forum with a little bit more info: https://devforums.apple.com/message/539344#539344

https://devforums.apple.com/message/588316#588316

Update: There is a better way. Just build your static library with iOS5 minimum target, and manually add /Developer/Platforms/iPhoneOS.platform/Developer/usr/lib/arc/libarclite_iphoneos.a (and /Developer/usr/lib/arc/libarclite_iphonesimulator.a) if your project is not using ARC and needs iOS4-support.

Update 2: Actually, just use the linker flag -fobjc-arc ; this will link libarclite with the library if it's not already in there. Best solution.

Answer 2

Wow that was a hard ride but i finally solved it!

What sparked the final idea was @steipete's comment , Its a bit of a complex situation so i'll try to explain it for anyone who might've crossed this issue as well.

1. Compiling a ARC-enabled framework on iOS 4.3 will automatically attach libarclite.so to "bridge" 4.3 ARC with 5.0 ARC. When this framework was imported to a 4.3 project, arclite was actually linked twice - once for the framework (which is 4.3), and once for the project itself - which caused the "duplicate symbol" error, meaning the framework has to be compiled on 5.0, and the project can be 4.3. But then ;
2. My framework is using @mattt 's AFNetworking to perform HTTP Requests and JSON parsing of different APis. AFNetworking automatically checks while compiling if your target is iOS5 , and if it is, it uses NSJSONSerialization, otherwise it would fall back to any imported JSON library such as JSONKit.
3. When compiling my AFNetworking-enabled Framework for iOS5 (to avoid problem no.1), it would automatically attach NSJSONSerialization, which will cause an exception on 4.3 projects, meaning you would have to manually look for the compile directions and remove the calls to NSJSONSerialization before compiling, so it would automatically fall back to the 4.3-compatible library (in my case JSONKit) . That compilation condition is found on AFHTTPClient.m and AFJSONRequestOperation.m (e.g. #if __IPHONE_OS_VERSION_MIN_REQUIRED > __IPHONE_4_3 || __MAC_OS_X_VERSION_MIN_REQUIRED > __MAC_10_6)
4. After removing those conditions, i successfully compiled my framework for iOS5 with JSONKit instead of NSJSONSerialization, and was successfully able to use it in my iOS4.3 project.

Hope this would help anyone else who might struggle with this for a couple of days like myself :)

Shai.