It's a weird situation for me that I cannot run my project on device or emulator but when I choose profile instead of run option, the app run flawlessly without any zombie guys.
It happens after I convert my project to ARC. I just modify code as Xcode tell me todo and due to the size of this project, I cannot look through every line of code.
ps. I'm the third hand on this application, so it's almost impossible for me to understand 10k lines of code.
Have you tried enabling Zombies in Xcode itself without profiling? This will set objects to never dealloc so that when you message an object that has a zero retain count, it will know what the object is and tell you. Just make sure you turn it on again so that objects will dealloc as normal.
See how to do that here:
How to enable NSZombie in Xcode?
the following can help you after the fact, but it's best IMO to perform them before migration; if a problem exists, ARC will solve some issues while abstracting others from you:
1) Create more Autorelease Pools one approach which might help you narrow things down is to explicitly create autorelease pools -- this can help localize some of your app's memory related issues. explicitly adding autorelease pools has other benefits, so this can be done not only for bug-seeking.
2) Use GuardMalloc as well, there are other memory related tools -- your app should also run fine with GuardMalloc enabled. switching to ARC could change the point of destruction -- you may be holding on to a dangling pointer.
3) Remove all Leaks finally, this may sound backwards -- remove all leaks possible. you want memory operations and lifetimes well defined. if you have an occasional leak, your issue could be hard to detect. oftentimes, reducing leaks can help you isolate the problem by making the problem easier to reproduce.
Related
I have found few memory leaks when I am running my application. For your reference, I am sharing the screenshots of Instrument debug logs and also Xcode Debugg memory graph tool. I am not getting what is going wrong here. Please help me to resolve memory leaks.
Please help me to fix the memory shows in the image. Thank you.
I know this is an old question, but a few observations.
When you have a lot of objects that are leaking, focus on high level objects (especially your own classes). We do not care why the array was not released. We care about why the item that is keeping a strong reference to it was not released. XTubeManager and GlueTubeManager are probably good places to start searching, but I don't know what other high level objects appear in the panel on the left.
When you have leaks, it is very useful to use the “Malloc Stack Logging” feature. So edit your scheme (command+<; or “Product” » “Scheme” » “Edit”) and go to the “Diagnostics” section and temporarily turn on “Malloc Stack Logging”:
Then, when you select a leaked object, you can see where it was instantiated but using the memory inspector panel on the right:
Look for entries in that stack trace that are white (your code), as opposed to all the system items that are in gray. When you hover items in that stack trace, there is even a little arrow that lets you jump to the code in question. In my example, the leaked object was instantiated in viewDidLoad.
This will not tell you why it leaked, but you will be able to see where the object in question was instantiated in your code, and you can start your investigation from there, diagnosing why an object created at that point in your code still has lingering strong references.
Remember to turn off the “Malloc Stack Logging” feature when you are done with your diagnostics.
As an aside, when we see URLSession objects that were not released, that begs the question of whether you instantiated a URLSession object (rather than using the shared instance) and neglected to call finishTasksAndInvalidate. Ideally, you would have a single URLSession and reuse it for all network activity (or use the shared instance), but if you must instantiate sessions, make sure to invalidate them when you are done.
You do NOT need to use Instruments. That's the old way. Use Xcode itself.
See Visual Debugging with Xcode
- 24:45
Watching the video is a MUST, but the summary of the video is as such:
There are two type of memory problems. You just have to repeat a flow in your app 2-3 times to be certain the memory graph has caught it
Leaks. Xcode will annotate this with purple icon. Possible are: delegates, closures
Abandoned memory. Xcode will not annotate this. But it's still increases your memory footprint. possible examples are: A repeating timer that is never invalidated, NotificationCenter, A never ending DispatchWorkItem
For Leaks the memory graph is a loop ie two way.
For Abandoned memory the graph is NOT two way. It's just an object one that Apple categorizes as 'root path' referencing your object and never letting it go. For more on this see here
In this case, just because some tool says you’ve got a memory leak doesn’t mean you have one. The amount of data seems to be less than 1MB, that’s nothing. Your tool suspects there’s a leak because data was allocated and not released, but these are single objects. Quite possible that memory is going to be released or reused later.
Use your software for hours and check if memory usage gets larger.
Memory on mobile devices is a shared resource. Apps that manage it improperly run out of memory, crash, and suffer from drastically decreased performance.
so to fix it follow this steps
Open Xcode and build for profiling.
Launch Instruments.
Use the app, trying to reproduce as many scenarios and behaviors as possible.
Watch for leaks/memory spikes.
Hunt down the source of the memory leaks.
Fix the problem.
Whenever I am using ASIHTTPRequest for making webservice calls I am randomly getting the following crash:
autorelease pool page 0x9418000 corrupted
magic a1a1a100 4f545541 454c4552 21455341
pthread 0xb0103000
My code is ARC-fied and used -fno-objc-arc for the .m files of ASIHTTP class.
Does anybody have an idea about this or did anybody face this kind of issue before? Thanks in advance!
This likely indicates that you're stomping memory somewhere else. I'd start by turning on memory diagnostics and looking for mistakes. The most likely place to cause these kinds of mistakes is in C code, particularly when using C arrays or C strings. You're probably writing outside of your allocated memory, or writing into memory after you freed it.
There have at times been compiler bugs that would cause this kind of problem, but these are very rare, and I would strongly suspect your code first.
As Rob pointed out, this is likely an indication that you're misusing memory elsewhere. To turn on memory management diagnostics as of Xcode 8:
Click the scheme menu in Xcode and choose "Edit Scheme..." at the bottom.
In the Run step, go to the Diagnostics tab.
Under Memory Management, turn on all four options. I generally find Guard Malloc to uncover the most problems but they can all be useful.
I've been researching this throughout SO and some people said that this error is fine as long as the apps doesn't crash.
My app gets this error and after this when I try to tap on a row for a cell (calling didSelectRowAtIndexPath) it crashes. And it gives me an error UIImage sent message to deallocated message. I am guessing that this is because of the memory warning it has freed up some UIView's and therefore it crashes.
Why is this and how do I fix this? I've been debugging this for quite some time, using instruments, profiling, etc and had no luck.
I'd like to post some code, but don't know which one to post.
You have failed to retain something you cared about. From your message, I would suspect the object is a UIImage. Start by running the Static Analyzer and see if you're unretaining something obvious. Then inspect your ivars, particularly ones that are related to images. Make sure you access your ivars using accessors and not directly (except in init, the accessors themselves and dealloc). Make sure your object properties are defined with "retain".
You can use the "Zombies" instrument to help you track down which object is under-retained.
by one of your comments, it is very clear that the issue is with memory management and releasing your objects.... I suggest you to go a bit deep into your code and find out the code snippets where you are releasing you objects(or allocating them)... It can also be due to the fact that you are not at all releasing your objects after allocating and the processor trying to kill your app due to the lack of memory...And by the way, this kind of erros suck your time a lot... good luck...
I have an iPhone app that is crashing without explanation. After reading that Autorelease pools are ill advised for iOS I went to search them out in my app and have discovered three (including one in main.m and one in a NSThread).
What exactly do I need to do to eliminate these from my code?
Thanks!
EDIT 1
I am printing, but can't see why it's crashing. Basically I start a thread which calls a method and then the app crashes. The first thing the method is set to do is to print to the console (with no values, just to show that the call worked), but it doesn't even get to that point. Very strange. Any ideas on how I could debug this?
Where did you read that autorelease pools are ill advised? I suggest you find some better sources of information.
Granted, you shouldn't be using autorelease pools haphazardly, and improper usage can cause problems, but certain situations require them. At a minimum, that one you found in main.m should be there. As should the one you found in your NSThread. It is very unlikely that they are responsible for your crash, assuming that your code is using them correctly.
When you application crashes do you get anything at all when running in debug mode? Any stack trace in the console, or log messages talking about memory warnings? Does the app crash randomly or only after performing a particular action? More information and/or code would be useful.
Autoreleases that are part of the iOS templates are not the problem. Autorelease pools are often necessary, and may not be why your app is crashing.
To address your problem
Add NSLog statements to your code to try and find out where your app is crashing
Use Instruments to detect memory problems and leaks
You may be over releasing objects. Here's an excellent Memory Management Guide.
Autorelease in main function and in new thread is required as per apple documentation. because when app launch some memory is reserved for launching the app. and if autorelease pool rempoved from the main function memory leak will be shown by simulator same in creating new thread.
Autorelease pools are required and the presence of an Autorelease pool is certainly not your problem. If your app is failing without a helpful log, try setting a breakpoint on exceptions.
http://developer.apple.com/library/mac/#documentation/IDEs/Conceptual/Xcode4TransitionGuide/Debugging/Debugging.html
Coming up towards the end of developing an iPhone application and I'm wondering just how bad is it to use autorelease when developing for the iphone. I'm faced with some fairly random crashes and, so far, I can't pinpoint it to anything other than sloppy memory usage.
As a Cocoa newbie I remember initially reading a guideline document that strongly suggested avoiding autorelease in favor of manual retain/release for iPhone. However, a more 'senior' Cocoa developer came on board early on (who ironically has been let go since), who used autorelease all over the place. Admittedly, I was went into "monkey see monkey do" mode, and it appears to be coming back to haunt me (I'm now the only developer on the project).
So what to do next? It seems to me that I have to branch the code and try to go through and replace, where possible, autorelease code keeping my fingers crossed that I don't inadvertently break the app. It seems a lot of library calls result in autoreleased objects like stringWithFormat and pretty much anything where I'm not using alloc myself. Any other gotchyas and/or suggestions I should be looking out for? Thanks Cocoa gurus.
Using release instead of autorelease can improve memory usage in tight spots (which is good on the iPhone), but it's not going to help at all with crashing if you're not following the retain / release rules. I would read a few tutorials on memory management in Obj-C if you're still a little hazy on what you should be doing, and then go after those crashes using the debugger and crash reports to find out where you're over releasing objects. This and this are two good places to start.
More important than the autorelease or manual-release choice is how often you alloc and dealloc your NSAutoreleasePools. Since most of the Cocoa frameworks use autorelease liberally, you need to have a proper pool draining strategy. Once that is in place, the choice of whether to release or autorelease becomes much less an issue.
That being said, the only areas you should worry about are tight loops--allocate and release an NSAutoreleasePool every few iterations for best results; and when you have spawned another NSThread that doesn't have a Runloop--create a pool and drain it every so often becomes idle. Since most applications only allocate a small amount of data per event, UIKit's strategy of allocating the pool before the event is dispatched and releasing it after the dispatch returns works very well.
If you think you dunno how to use autorelease, check out CS193p FALL 2010 on iTunes U -> Lecture number 4.
It teaches you all about memory management and stuff (if you skip the first 10 minutes or so)
For iPhone performance reasons, Apple suggest that, whenever possible, you shouldn't use autoreleased objects. Instead, explicitly release your objects when you are done with them.
Using autorelease pools means that you might be leaving some unused memory lying around. Since the iPhone has less memory to go around, you might improve performance if you free up unneeded memory as soon as possible, rather than letting it sit around taking up resources while it waits for an autorelease.
When you autorelease, you're basically saying: "I don't need this any longer, but anyone else is free to pick it up (before the auto release pool is drained)". When you explicitly relase an object you're saying: "I don't need this any longer and unless anyone else has already said otherwise (acquired), it should be deallocated immediately."
Consequently, autorelease is not normally the wrong thing to. It is required when you want to pass objects back to the sender of a message without requiring the sender to take care of releasing the object.