How to diagnose ANE crash on startup?

Question

We have an ANE which when used causes the app to die on startup. This happens on an iPhone4 device running iOS5. As far as we can tell, the app is crashing before it enters AS code, and way before the ANE is actually used. Even if the ANE is not referenced, including it in the build will still cause it to crash on startup.
The ANE is compiled against iOS6 SDK, but deployment target is 4.3.
It is using linker options to add the frameworks for Social, Accounts, and AdSupport
Compiler is building just for armv7 (not armv7s).
Packaged with Air 3.4.
App will package and deploy to device fine, but will not launch. Have tried various build configurations to no avail. Not really sure how we can go about debugging this?

Answer 1

Are you using weak linking to link with frameworks which are not available on the device? Social framework is not available on iOS 5. If not, your crash log will show errors like "dyld: Symbol not found: XXX Referenced from: YYY Expected in: ZZZ". When you link your app against a framework and then deploy it on a platform where that framework is not available, it crashes because the loader doesn't know how to resolve the symbols from that framework. If, for example, your app uses Twitter framework it will not run on older platforms directly. The solution is to use weak linking for the framework and guard calls to symbols in that framework with checks for availability. To use weak linking specify "-weak_framework Twitter" instead of "-framework Twitter" in your platform options file. Guard calls to the Twitter APIs like this:
If ([TWTweetComposeViewController class] != nil) {
                // TWTweetComposeViewController is available
                // use API
To see compiler warnings about newer symbols when building set the target SDK to 5.0 in your Xcode project for the native library. Then you should see compiler warnings saying " warning: definition for 'XXX' not found" or something similar.
Hope this helps.
~rajorshi