I've developed my application using my 3G device to test with. Upon giving this to a friend to test, he's noticed that it crashes..I've had a look at the crash log, but it's not much use except for the "EXC_BAD_ACCESS" statement after a few memory warnings.
On my device, I can use the imagePicker lots, and each time a photo is taken I get a memory warning, but this doesn't cause any problems.
On my friend's device (also a 3G), after a couple of images chosen from the camera, the app crashes.
So, my question is.. I think something is being deallocated because of the memory warning - but only on my friend's device, and then after deallocation, it's trying to be used again. How can I find out what object is being called? I can't use NSZombies because this is a remote (beta) device.
Help please!
Also if anyone has any ideas why my device can pick image after image without any problem and his can't...that would be most helpful
Thanks!
EDIT: New discovery.. I'm getting this error message too: KERN_PROTECTION_FAILURE which I understand to be something to do with data access. The crash seems to happen right after I save the image got from the UIImagePicker. Any ideas?
You may be over-releasing something. If you're running Snow Leopard, run the Static Analyzer (Cmd-Shift-A) and look for memory errors.
The fact that it crashes after a memory error suggests that a UIViewController has released its view. Do you have any UIViewControllers that observe NSNotifications, or otherwise might change their IBOutlets while they are off-screen? This is a common cause of this kind of crash. Make sure you're correctly memory managing your IBOutlets. UIViewControllers should never mess with their IBOutlets (or their UI components at all) when they are off screen. Even if you don't make this mistake, if you're not implementing things as noted in the above link, you can still crash after memory warnings.
MemoryWarning was a pretty good idea, and things have improved, but Apple still hasn't quite cooked all the issues around how it plays with UIViewController. The developer still needs to be very careful.
You should have your friend come to your computer and run it with NSZombieEnabled. That's the best way to debug these issues.
Related
I created a test project to confirm my memory leaks:
Project file: https://dl.dropbox.com/u/3703182/PickerView.zip
Basically a UIPickerView is connected to a datasource via IB. When it's connected to a datasource, it leaks. If not, no leak. I need to use a UIPickerView for an imminent app that needs to be released ASAP, unfortunately it guarantees a crash every 2 hours because of the leak. How can I use the UIPickerView despite the memory leaks without crashing?
EDIT:
It only leaks on device, not in simulator.
That is not a leak. It's an allocation.
If it was a leak it would show a red spike in the second row.
The real test for a leak is presenting and dismissing several times over. If you can do that and show that the allocations keep rising then there is a leak. Not otherwise.
Adding my comments as answer,
Your app will not crash due to this leak since it is a very small leak caused by framework which you dont have to worry about. The screenshot shows that it is in terms of a few bytes. If your app is crashing every 2 hours, that means there is something else which is using a lot of memory. Please check if you are using anything else in your code which could cause this and update the question with your finding.
In allocation tool, make sure you are checking the live bytes section and check how much it is going up. If it stays below 15-20 MB, you dont have to worry much anyways. Check this for more details about memory usage in app. Also check this XCode Instruments Allocations: Look at Live Bytes or Overall Bytes?.
This is the Apple library that is leaking. You cannot do anything about this. It is Apple's fault.
This isn't a leak you can control, it's internal... but this is a very small amount of memory and will not crash your application. I'd be interested in seeing what this looks like an hour in... Can you provide a backtrace of the crash? That would probably better help determine the real cause of the crash.
I have some code that returns a struct containing 2 objects (declared as id).
When trying to use one of the objects I get an EXC_BAD_ACCESS and the app crashes. This only happens on the device (ipad) not in the simulator.
I have set NSZombieEnabled to YES, however no information is written to the console.
I don't know if it's a problem that I'm using a workspace in Xcode 4, one project for my app, and another that builds a library which is used in my app. The EXC_BAD_ACCESS is occurring in the second project, so I don't know if NSZombieEnabled will apply to the second project?
How do I solve this? Especially as I it only happens on the device (even goes as planned on the simulator), and it is in the second project?
EDIT: This is the method where the EXC_BAD_ACCESS occurs, on line 62, on sortRange.lower –
NSZombieEnabled only works on the simulator, not on the device, so it's probably hiding the problem. Run Product > Analyze (⇧⌘B) for clues. It's harder to say more without looking at the code. As Mihai says, your objects are probably over released, which is the most common cause of EXC_BAD_ACCESS.
It seems that one of your objects is autoreleased before you are trying to access it. As the iPad has less memory than the computer you are running it on it get's released faster so that's why it's not available. Try NSLog both objects just before the line you are getting the error and see wich one of them is the problem and than trace back to it's origin and retain it somehow. Also don't forget to release it after you are done using it. Some example code would be useful.
I am using the UIImagePickerViewController to take a photo in my app, but in iOS4+, which supports multi-tasking, I encountered a memory problem. If you've opened a lot of apps, and then mine, the UIImagePickerViewController does not work properly anymore. The picker controller some times get closed without calling the delegate method, sometimes the whole app crashes. Of coz, the memory warnings are already received, but what can I do? Dismiss the pickerController when receiving the 1st memory warning, and alert the user that he has to kill as many suspended apps as possible and retry? This is really not a nice user experience? But if I do not do so, a crash or a sudden close of the pickerController also confuses the user. Did anyone meet and solve the same problem?
UIImagePickerViewController is notorious for throwing memory warnings. If you don't want to be in the business of making sure everything is ready to unload if you get those warnings then I recommend you switch to AV Foundation instead.
This SO answer has a link to a tutorial which may get you started in that direction.
AVFoundation camera tutorial
I am getting a lot of strange EXC_BAD_ACCESS crashes on the iPad that only happen on the device and not in the simulator. I am assuming that they are somehow memory related, but I am not sure. They all happen with image context related functions.
One strange example is using CGImageCreateWithImageInRect. For example, if i run through a bunch of UIImages and crop them with CGImageCreateWithImageInRect, it will always crash at specific arbitrary sizes. Like, if I crop them all to 200x200, it crashes out after processing 12 images. If i crop them to 210x210, it works no problem.
The EXC_BAD_ACCESS happens inside of "memmove" called from "CGBlt_copyBytes". That is all the debugger shows me strangely enough. I can't see the callstack going up to any of my methods.
All of this works fine in the simulator!
I know this is all very vague, but if anyone has any ideas, they would be greatly appreciated.
Start by doing things like checking for zombies, and running clang (Build & Analyze) to see if you have memory management issues. I think you'll need to post more code, because this does sound like memory stomping.
I have an app that has a tabBar Controller and a navBar Controller. It has ~8 views (a variety of web, table, standard, mail, address etc.), some created using IB some created using XCode to make the table views. I've ran the memory leak tester and it doesn't have memory leaks. It can crash at anytime on any of the views, If I flip back and forth between views and use some of the functions it closes the app.
I assume that either I am running 1) out of memory or 2) not releasing views correctly, which causes the app to close. The app is simple so I don't know how I could be out of memory and I've reviewed the code to the best of my ability for releasing the objects correctly.
So Here is my list of questions:
1) What and How to use some of the other debugging tools (or tell me what tools/files I should be looking for using)? I would like to narrow down the problem to its source.
2) What is the best practice for releasing these views? How?
3) How much memory do normal apps use? Is there a number that I should stay around? How do I verify that in the simulator? the Allocation tool?
Feel free to point me to apple docs or other stackoverflow questions that can help me.
UPDATE: It appears to only be crashing one view is used, which has a table view with custom cells... The cell are populated from a plist file... this view worked fine a few days ago, I notice that some cells do not have data from the plist file... it could be a plist file problem with not storing proper data. I'll continue to work on it.
UPDATE #2: I went back to older rev of my files, to when this particular tableView worked just fine (pre 3.0) and guess what it works just fine, I change the simulator to 3.0 with this rev of the app and bam crash on this tableView shows up. Thanks for the help so far, I'll try somethings mentioned below and let you know what I find. If you have some tips on why a tableView w/custom cells from 2.2.1 to 3.0 would start crashing, I'll take them. If I can't get anywhere I'll post the code soon. BTW, I mis-spoke above, I thought it wasn't crashing in the simulator... I was wrong it is.
Solution: thanks for the troubleshooting tips the fix was quite simple, but it's odd it didn't crash in 2.2.1... it should have crashed a long time ago for the problem, I was releasing an object one to many times in my custom cell... duh.
On the first and second generation phone's you really don't want to be going over about 20 megs of real memory usage - once you get over that you are at risk of being killed by springboard.
One of the big culprits I've seen is autoreleased memory, since the autorelease pool can hold onto memory a lot longer than you would really like - if you are using a lot of autoreleased objects that can be a potential problem. You can improve this by doing more explicit retain/release where possible and by creating local autorelease pools manually and releasing them after doing a more intensive operation with a lot of autoreleased objects.
The most effective way to keep track of real memory usage I've found so far is running a debug build on a test phone and running with Activity Monitor. That will give you a clear idea of how much memory is getting taken and held onto by your app. As well as how much is being used when it crashes on you.
You can run with Activity Monitor in Xcode on the Run menu -> Start With Performance Tool -> Activity Monitor.
One other very useful tool is the CLang Static Analyzer that you can run against your code base and can give some very helpful memory management information. As mentioned here.
One thing I would try is putting some debug messages into your didReceiveMemoryWarning method(s). That way, if you are running out of memory, you'll at least have some warning.