How to configure a universal app which must run on iOS 5.1.1 such that it also runs with 64 bit on iPhone 5S?

Question

With Xcode 5.0.2 I try to run and profile an app on an iPad 1 running iOS 5.1.1. The app is universal and based on a modern template. Deployment target is iOS 5.

To my understanding Apple expects that developers include 64-bit versions in their apps and when they do, the app bundle has 32 and 64 bit code. It seems that if your app targets iOS < 6 it can't include a 64 bit version.

So what does that mean? Must I remove the 64 bit support and will my app then run slower on a 5S? Or is there another way to ship bith 32 and 64 bit and still support iPad 1?

Answer 1

The short answer is, you can't.

Unfortunately 32/64 bit "fat" applications will only run on iOS 6 (I think it may even be 6.1) Previous iOS versions don't know how to read the fat binary file format.

We went through this when we had to release an update to our free app, Face Dancer . It uses face detection, and face detection is broken for 32 bit apps on the iPhone 5s and iPad air.

The previous version in the app store worked on iOS 5 and up, but we had to drop iOS 5 support in order to make a 32/64 bit build.

By the way, most apps don't need to care about 64 bit code. It's only if you're doing heavy number-crunching or heavy-duty graphics (which amounts to the same thing) that you'll notice any difference at all.

Answer 2

Set deployment target to 6.0 while you profile. Be sure to reset it before submitting to AppStore.