How do I set up NSZombieEnabled in Xcode 4?

Question

How do I set up NSZombieEnabled and CFZombieLevel for my executable in Xcode 4?

Desman

are you asking about Xcode 4? – Tizes

Why options like this isn't enabled by default is beyond me... – Belton

Because it basically prevents any real freeing of memory, which doesn't seem like a good idea to enable by default. – Desman

@Daniel Magnusson: it's a survival-of-the-fittest thing. By making development with XCode unfriendly but workable, you get better devs. Just kidding. – Plectrum

@DanielMagnusson I think this is not a bad idea, AFAIK the "Zombie" mode will change every object to a special kind ob object so that it can detect, when it gets sent messages. So having "Zombie mode" enabled will cause that no object will ever be deallocated, so you should really only used it when tackling such errors. – Rambunctious

Answer 1

In Xcode 4.x press

⌥⌘R

(or click Menubar > Product > Scheme > Edit Scheme)

select the "Diagnostics" tab and click "Enable Zombie Objects":

This turns released objects into NSZombie instances that print console warnings when used again. This is a debugging aid that increases memory use (no object is really released) but improves error reporting.

A typical case is when you over-release an object and you don't know which one:

• With zombies: -[UITableView release]: message sent to deallocated instance
• Without zombies:

---

This Xcode setting is ignored when you archive the application for App Store submission. You don't need to touch anything before releasing your application.

Pressing ⌥⌘R is the same as selecting Product > Run while keeping the Alt key pressed.
Clicking the "Enable Zombie Objects" checkbox is the same as manually adding "NSZombieEnabled = YES" in the section "Environment Variables" of the tab Arguments.

Kaliope

Thanks - I was wondering where they hid these options.I now realize this is the same window as in the 'Edit Scheme' menu. – Publea

Just to add to this, doing it in the "Run" screen sets it for "Test" as well if the "Use the Run action's options" box is checked. If you want to do it for just Test, that box needs to be unchecked – Erna

Please also note that this option appears on Xcode 4.1 (right?) – Aquarium

In XCode 5 (and later versions of 4 -- 4.3.x for sure, maybe earlier), this is CMD-< (CMD-SHIFT-comma), or Product -> Scheme -> Edit SCheme... – Breland

i do prefer this to running profile and then using zombie instruments - seeing the actual message sent was the key to solving the problem, for me – Evoke

I am stuck in strange EXC_BAD_ACCESS issue, even the Zombies are skipped, it would be nice if you could direct me for this #29210557 – Outport

Answer 2

Jano's answer is the easiest way to find it.. another way would be if you click on the scheme drop down bar -> edit scheme -> arguments tab and then add NSZombieEnabled in the Environment Variables column and YES in the value column...

Firebox

Answer 3

I find this alternative more convenient:

1. Click the "Run Button Dropdown"
2. From the list choose Profile
3. The program "Instruments" should open where you can also choose Zombies
4. Now you can interact with your app and try to cause the error
5. As soon as the error happens you should get a hint on when your object was released and therefore deallocated.

As soon as a zombie is detected you then get a neat "Zombie Stack" that shows you when the object in question was allocated and where it was retained or released:

Event Type    RefCt     Responsible Caller
Malloc            1     -[MyViewController loadData:]
Retain            2     -[MyDataManager initWithBaseURL:]
Release           1     -[MyDataManager initWithBaseURL:]
Release           0     -[MyViewController loadData:]
Zombie           -1     -[MyService prepareURLReuqest]

Advantages compared to using the diagnostic tab of the Xcode Schemes:

1. If you forget to uncheck the option in the diagnostic tab there no objects will be released from memory.

2. You get a more detailed stack that shows you in what methods your corrupt object was allocated / released or retained.

Rambunctious

"Zombies" option is missing in my XCode 4,why? – Macaulay

Make sure you're choosing iOS Simulator > All from the main template list (You can only do this in the simulator) – Rambunctious

for some reason.. if i select 'zombies' it just shows allocations.. any idea why? – Lefton

Answer 4

In Xcode 4.2

• Project Name/Edit Scheme/Diagnostics/
• Enable Zombie Objects check box
• You're done

Calends

Answer 5

On In Xcode 7

⌘<

or select Edit Scheme from Product > Scheme Menu

select Enable Zombie Objects form the Diagnostics tab

As alternative, if you prefer .xcconfig files you can read this article https://therealbnut.wordpress.com/2012/01/01/setting-xcode-4-0-environment-variables-from-a-script/

Naissant

Answer 6

Cocoa offers a cool feature which greatly enhances your capabilities to debug such situations. It is an environment variable which is called NSZombieEnabled, watch this video that explains setting up NSZombieEnabled in objective-C

Gullible

Answer 7

In Xcode > 4.3:

You click on the scheme drop down bar -> edit scheme -> arguments tab and then add NSZombieEnabled in the Environment Variables column and YES in the value column.

Good Luck !!!

Monachism