How Single App Binary Supports 64-bit and 32-bit Apps

Question

We can see apple announcement here.. According to this doc, we can submit same binary with supporting 32-bit and also 64-bit. I found one stack overflow answer here. But Accordi

Answer 1

Xcode can build your app with both 32-bit and 64-bit binaries included so it works across all devices running iOS 7. If you wish to continue to support iOS 6 then you will need to build for 32-bit only. Next month we will be making changes that will allow you create a single app binary that supports 32-bit on iOS 6, as well as 32-bit and 64-bit on iOS 7.

Converting Your App to a 64-Bit Binary

At a high level, here are the steps to create an app that targets both the 32-bit and the 64-bit runtime environments:

1.Install Xcode 5.0.1.

2.Open your project. Xcode prompts you to modernize your project. Modernizing the project adds new warnings and errors that are important when compiling your app for 64-bit.

3.Update your project settings to support iOS 5.1.1 or later. You can’t build a 64-bit project if it targets an iOS version earlier than iOS 5.1.

4.Change the Architectures build setting in your project to “Standard Architectures (including 64-bit).”

5.Update your app to support the 64-bit runtime environment. The new compiler warnings and errors will help guide you through this process. However, the compiler doesn’t do all of the work for you; use the information in this document to help guide you through investigating your own code.

6.Test your app on actual 64-bit hardware. iOS Simulator can also be helpful during development, but some changes, such as the function calling conventions, are visible only when your app is running on a device.

7.Use Instruments to tune your app’s memory performance.

8.Submit an app that includes both architectures for approval.

The remainder of this chapter describes problems that frequently occur when porting a Cocoa Touch app to the 64-bit runtime environment. Use these sections to guide your own efforts to investigate your code.

From https://developer.apple.com/library/ios/documentation/General/Conceptual/CocoaTouch64BitGuide/ConvertingYourAppto64-Bit/ConvertingYourAppto64-Bit.html#//apple_ref/doc/uid/TP40013501-CH3-SW1