NSZombies to the rescue... finding your EXC BAD ACCESS memory issue

Anyone who has developed a native application for iOS will have encountered the dreaded EXC BAD ACCESS error with zero information about what caused the crash.

NSZombies catches attempts to access deallocated objects (which are the primary causes of that error) by replacing the deallocated object with a zombie.

When a zombie is accessed a helpful message is logged to the console: message sent to deallocated instance

Take a read of Finding Memory Leaks for instructions on how to activate NSZombieEnabled on your Debug executable.

Make sure you only activate NSZombies on your Debug executable as you don't want to release an application that never frees memory.

Using Xcode Targets for Adhoc iTunes Artwork

By creating multiple Xcode targets you can adjust what files are included in each target.

eg iTunesArtwork for adhoc users or testers

As the iTunesArtwork file only works for adhoc builds you want to exclude it from debug and release builds.

To create an Adhoc target which includes your iTunesArtwork  file you need to:

• Create a new Adhoc target
  
• Add your iTunesArtwork file to your project
  
• Change the target memberships for your iTunesArtwork

Step by Step:

1. Duplicate the primary target (right click -> Duplicate)
   
2. Rename the new target to Adhoc
   
3. Add your iTunesArtwork file to your project as described here
   
4. Change the target memberships for your iTunesArtwork file to Adhoc only using:
   Select Target -> right click -> Get Info -> Targets
   (make sure only Adhoc is selected)

Once you've made these changes you can explore the Target build phases. The iTunesArtwork file should only appear in Copy Bundle Resources for the Adhoc target.

It may be useful to have matching targets and configurations for each type of build eg

• Debug
• Adhoc
• Release 
  

When changing the build type set both the active configuration and active target.

Other uses for multiple targets include:

• Different icons for Debug / Adhoc / Release builds
• Incrementing build numbers only for Adhoc / Release builds

Identifying the Current Xcode Configuration

The easiest way to identify the current configuration in code is by creating a preprocessor macro under your Xcode project build settings.

Step by step:

1. Project menu -> Edit Project Settings -> Build tab
2. Select All Configurations
3. Scroll down to GCC 4.0 - Preprocessing
4. Add the following to Preprocessor Macros Not Used in Precompiled Headers:
   
   CONFIGURATION_$(CONFIGURATION)

Assuming you have Debug, Adhoc and Release configurations, this will generate preprocessor macros for each configuration. ie

• CONFIGURATION_Debug
• CONFIGURATION_Adhoc
• CONFIGURATION_Release

In your code you can now use something like:

#ifdef CONFIGURATION_Debug

NSLog(@"Debug message");

#endif

#if defined (CONFIGURATION_Debug) || defined (CONFIGURATION_Adhoc)

NSLog( @"Warning message");

#endif