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…
Related
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 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.
Options:
1) When there is bad input, the app crashes and prints a message to the console saying what happened
2) When there is bad input, the app throws away the input and continues on as if nothing happened (though nothing the problem in a separate log file).
While 2 may seem like the obvious solution, the app is an engine and framework for game development, so if a user is writing something and does something wrong, it may be beneficial for that problem to be immediately obvious (app crashing) rather than it being ignored and the user potentially forgetting to check the log to see if there were any problems (may forget if the programmed behavior isn't very noticeable on screen, so he doesn't catch that it is missing).
There is no one-size-fits-all solution. It really depends on the situation and how bad the input is.
However, since you specifically mentioned this is for an engine or framework, then I would say it should never crash. It should raise exceptions or provide notable return codes or whatever is relevant for your environment, and then the application developer using your framework can decide how to handle. The framework itself should not make this decision for all apps that utilize the framework.
I would use exceptions if the language you are using allows them..
Since your framework will be used by other developers you shouldn't really constraint any approach, you should let the developers catch your exception (or errors) and manage what to do..
Generally speaking nothing should crash on user input. Whether the app can continue with the error logged or stop right there is something that is useful to be able to configure.
If it's too easy to ignore errors, people will just do so, instead of fixing them. On the other hand, sometimes an error is not something you can fix, or it's totally unrelated to what you're working on, and it's holding up your current task. So it depends a bit on who the user is.
Logging libraries often let you switch logs on and off by module and severity. It might be that you want something similar, to let users configure the "stop on error" behaviour for certain modules or only when above a certain level of severity.
Personally I would avoid the crash approach and opt for (2) that said make sure that the error is detected and logged and above all avoid any swallowing of errors (e.g. empty catch).
It is always helpful to have some kind of tracing/logging module, for instance later when you are doing performance tuning or general troubleshooting.
It depends on what the problem is. When I'm programming and writing error handling I use this as my mantra:
Is this exception really exceptional?
Meaning, is the error in input or whatever condition is "not normal" recoverable? In the case of a game, a File not Found exception on a texture could be recoverable and you could show a default texture so you know something broke.
However, if you have textures in a compressed file and you keep getting checksum errors, that would be an exceptional exception and I would crash the game with the details.
It really boils down to: can the application keep running without issue?
The one exception to this rule though (ha ha) is, if something is corrupted you can no longer trust your validation methods and you should crash as quickly as you can to prevent the corruption from spreading.