Xcode continuously crashes given thread 1 exc_bad_access (code=2 address=0x8)

Question

after researching this error i have noticed it is code specific but any project i attempt to make, load, etc keeps giving me the same error and is always citing different parts of the code with this error message but because of the initial programs i setup, that have the exact default code nothing less nothing more and still receive the same errors i wouldn't see how adding my error log could help. Note this error occurs when using sprite kit in Xcode 5 and am running this on os x 10.8.5 thanks ahead of time for your patience, insight and hopefully an answer.

Solution

exc_bad_access is usually caused by what's known as a dangling pointer - accessing an object that has already been deallocated.

To debug this, enable zombie objects by either:

• Xcode : Edit the scheme and choose the 'Enabled Zombies' checkbox

• AppCode : Edit the run configuration and set the environment variable NS_ZOMBIE_ENABLED=YES

Spend some time to learn the Objective-C reference counting memory model - retains, releases, retain-cycles and autorelease pools.

You need to ensure that your object is being retained for as long as its being used. In ARC (Automatic Reference Counting - the default for iOS) this usually means setting a property or ivar for any object that will be used accross multiple classes - designating one object as the 'owner' of this object. It will then be deallocated along with the object that 'owns' it.

A good way to get an understanding of the Objective-C memory model and the way ARC works, is to try using manual memory management on a pet project (something with at least 2 or 3 view controllers). Once you're comfortable with manual-memory management, ARC will be super-easy, as well as save you time, typing and prevent forgetting to release an allocated object. Most/all Objective-C fundamentals books will cover memory management. (I've forgotten the name now of the one that I read).

A Common Cause

Let's say you have a UIViewController and a View that you'd like to present from within your current view controller. . . its allocated as follows:

UIViewController* anotherController = [UIViewController make];
[self.view addSubView anotherController.view];

'anotherController' will now be deallocated because its no longer used. If anotherController.view has unsafe_unretained references to anotherController it will cause an exc_bad_access.

Infinite Recursion:

Another cause of EXC_BAD_ACCESS is infinite recurssion, which can be debugged by adding some log statements - it will soon become apparent then!

Comments

[mhamer13]

thanks and i will look into that. also if you could please upload an a simple example it will go a long way.

[Jasper Blues]

Nice - please raise another more specific question if you get stuck along the way.

[MoralCode]

@JasperBlues Xcode : Edit the scheme and choose the 'Enabled Zombies' checkbox - How do you do this?

[Jasper Blues]

@Computer_whiz123 I added a picture. Click drop-down top left, choose edit scheme.

[MoralCode]

Does that checkbox only apply to objective-c? Or does it work with swift?

[Jasper Blues]

Swift uses the Objective-C runtime so it will apply as well. All Swift instances are ObjC instances (either fully fledged, with dynamic dispatch (Cocoa classes) or stripped down ones for systems programming (non NSObject subclasses). . in either case still applies.

[xhinoda]

this is very good explained.. but in my case i just clean and re-build again solved my problem. Note: I use swift 4, xcode 9.2 and my problem cause by a struct.

[fedterzi]

Thanks @xhinoda, I had the same problem, I wonder what may cause this and why cleaning the build folder fixes it?

[Merricat]

Same: cleaning build folder fixed it for me