I wrote an entire app, and I was just about to submit it to the app store, and in my final testing, I went back and added a few releases to ensure proper memory management was observed. And since then, I keep getting these random crashes. I've tried removing some or all of the release calls, I've tried retaining objects. I cleaned the project. I used NSZombieEnabled and that also is not helping. All this to not avail.
Most of the time, the console says provides no help. Usually the app loads, I put NSLogs in viewDidLoad, viewDidAppear, and viewWillAppear, and they all show up in the console, then it crashes.
Sometimes I also get EXC_BAD_ACCESS (and I know what that means). But its occurring randomly. So this doesn't make sense to me. Thanks for any help possible. I've written this whole app, and spent months on it. So I'm really stuck. Thank you.
Have you tried Build --> Analyze? It will search your code for leaks and other useful things you might have missed. Try that and see if it finds anything for you.
I agree with Rudy. It sounds like you're releasing something that is still in use. I would go back to the version that was working and start adding the releases one at a time til it causes the crash. Slow but effective debugging.
When you say that you "sometimes" get EXC_BAD_ACCESS, what do you get the rest of the time? Where does the crash stack indicate you're crashing? What messages do you get?
Random crashes usually indicate a timing problem. A common cause is accessing things on multiple threads. Are you? It can also mean timing differences based on network traffic.
Make sure the console doesn't indicate an exception rather than a memory violation. Usually there's something in the console that will be useful.
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I've not worked on this project in quite some time.. When I left it some time in the iOS 8s it ran just fine, however.. on the latest XCode I'm getting many inconsistent EXC_BAD_ACCESS crashes. Now afaik it's requiring a deallocated object. However, the error is lacking where to look. This is quite a big project and like I say, the errors are inconsistent.
I've tried enabling zombie objects, as well as passing it as a starting parameter. However, this is leading me to no joy. I'm expecting something in the debug console with zombies enabled, is this right?
If anyone has any tips on how to find an easier way to debug this, as opposed to tinkering with everything and hoping it works..
EXC_BAD_ACCESS just means that your app is trying to access an invalid memory address. While it is oft caused be a deallocated object, that isn't always the case.
When the app crashes, there should be a crash log or backtrace. Post it as that'll provide clues.
Lovely; a crash entirely in framework code. Seeing as how it is SceneKit that is crashing, I would suggest replacing any graphic assets with new ones and see if that fixes it (even if it doesn't look right). Then check to make sure all of your geometries and layouts are correct.
Have you tried adding a global Exception or Symbolic breakpoint? Those usually help me 99% of the time when I encounter issues without any sort of backtrace.
In other words, should a production app eliminate all logging and printing to the console to reduce memory usage (or is the memory usage negligible)?
In general logging take some very small amount of device resources but it is so small that you shouldn't feel any changes unless you are printing a whole book to console ;)
Despite of this, I would recommend to remove all your logs if they are not provide any valuable information to user. Pure debug logs could be very annoying and if someone will work with your code in future, he can call you unprofessional ;)
I will recommend removing logs in methods which are called frequently due to the nature of the app (e.g. an update method in a game loop). In such methods one println may cause noticeable stuttering.
You can use a method for logging which will print only in debug (scheme-wise) and do nothing on a release scheme.
You could keep your logs in debug builds, but you better disable them completely, there have been some apps that printed passwords, tokens to the log, which isn't the best thing to do,
I've got an app that gets information from a SOAP web service and I want to display the results in a UITableView.
I had a previous version of this app and I'm creating a new version to basically clean things up and get rid of a bunch of legacy code that's deprecated and no longer used.
In the previous version, this worked well. In the new version, not so much.
Basically, the current scenario is returning 3 strings that I'm trying to use as the basis for the data in my UITableView.
I'm struggling with this issue because it's so stinkin' hard to track down EXC_BAD_ACCESS errors!
(Parenthetically, if someone has a way to make the debug experience more like Visual Studio, I'd love to hear it! It's so frustrating to not have any idea which line caused the error, and also to not be able to look through my local variables at the time of the crash to see what's what. I've already added in the exception breakpoint, but that doesn't seem to do much.)
Anyway, the line that's causing the error APPEARS to be:
return [[self Libraries] count];
It occurs in tableView:numberOfRowsInSection:.
The error message I get APPEARS to reference a string that should be stored in the NSMutableArray [self Libraries].
What's going on here?
I'm using ARC, so shouldn't all of my memory management be correctly handled?
I don't have any manual release statements in my code ANYWHERE!
Please help me fix this!
Set NSZombieEnabled, MallocStackLogging, and guard malloc in the debugger. Then, when your App crashes, type this in the gdb console:
(gdb) info malloc-history 0x543216
Replace 0x543216 with the address of the object that caused the crash, and you will get a much more useful stack trace and it should help you pinpoint the exact line in your code that is causing the problem.
See this article for more detailed instructions.
ARC relies on the Apple standard/recommended naming practices. Check that you are not violating any of them.
Just for starters, if "Libraries" is an instance there are are naming issues.
OK, so I feel a little bit silly, but I've got two production machines. On one of them, I had installed a copy of Xcode 4.2 beta alongside the final, production copy. I forgot to uninstall the beta copy and was using it to run my code. As soon as I cleared that up and ran my code against the final, released Xcode 4.2, all works fine again.
As I mentioned to Jonathan Grynspan above, I DO understand Obj-C memory management. For some reason, I was getting a retain/release/release (performed by ARC), and that bug is remedied in the final version.
Thanks for the help in tracking this down! At least I got a definitive answer to WHY the problem existed!
I'm working on a tweak using captainhook.
I did something like:
[self.delegate somemessage];
//the message is a private api. I don't know its implementation detail.
and then the app used up a lot of system resources and got killed minutes later.
the problem is none of logs, errors or exceptions can be found in console. there is only a LowMemory crash report.
I'd like to know what's the possible causes of that, how can I deal with it?
I dont have even the least idea where to start to debug it…
I am working with a free app that calculates grades for norwegian high school students. The different subjects are stored in a sqlite database. Everything works fine, except for one thing: If i close the app and restart quickly (faster than, say, one second), it crashes. Also, this only happens if I close the app in specific circumstances involving selecting/checking subjects in a UITableView (the changes are immediately stored in the database). Anyway if I wait for more than one second before restarting the app, it never crashes.
The error is not traced in any way in the console window.
Instruments has found some memory leaks in my app, but they are very small (16 bytes). I presume that is not the reason for the crash (but I will try to stop the leaks). I have also tried deleting and reinstalling the app, and turning the iPod/iPhone on and off. No change...
I understand that I cannot ask anyone to find the error in the extensive code of my app. My questions to you guys are:
Have any of you experienced similar errors? Related to sqlite?
Do you think App store will reject the app because of this?
Does anyone have any idea where to start looking for the error?
I am very thankful for any response!
When you say "it crashes," what is the actual error you get in the stack on the phone? Is it an actual crash, or are you getting a "failed to launch in time error?"
On iPhone, it's possible for an app's main thread to terminate while still running background nondetached threads. In this sense, despite all the claims that you cannot run in the background, you actually can... for a few seconds. When the main thread terminates, you go back to Springboard, and eventually the OS will kill your process if it doesn't terminate on its own. Do you manage any of your sqlite work on a background thread? Do you create any nondetached threads (this generally requires pthreads, so if you don't know, you probably aren't, but sqlite might; check in Instruments).
It's possible that your last instance still has a lock on your database, and that your re-launch doesn't react well to that lock. Do you have proper error handling around your open?