Memory crashes in iOS with real memory usage only at 5megs

Question

I have been hunting down memory leaks for some time in my app. As of right now, as I flip back and forth between two views while watching the memory monitor instrument, the real memory fluctuates between 5 and 6 megs. This is all fine -- as far as I can tell everything is getting released properly when I pop back off a view. However, the virtual memory continues to increase and my available real memory drops rapidly every time I push the view back onto the view stack (even though the real memory usage of the app isn't increasing). Eventually, this all leads to an out of memory crash. Is this a telltale sign of any specific issue, or am I just missing a memory leak somewhere?

EDIT: The odd part is, I get an out of memory crash while the app is still only using up about 5 megs of real memory.

Answer 1

Have you used the "Leaks" Performance Tool? And check out the logs in Organizer to see if there's anything there.

Also look into the dealloc for the view controllers and make sure you are properly releasing all of it's objects?

Answer 2

Anyway, you can also use the "Build -> Build and analyze" option to find suspicious non-conventional code.

Answer 3

Do not use -retainCount.

The absolute retain count of an object is meaningless. It is an implementation detail. It may be influenced by many factors well beyond your code.

You should call release exactly same number of times that you caused the object to be retained. No less (unless you like leaks) and, certainly, no more (unless you like crashes).

See the Memory Management Guidelines for full details.

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In this specific case, you are leaking memory but in a way that leaks can't find it. The objects that are leaked are still connected to your overall application's object graph somehow. Maybe through a notification, maybe through delegation, doesn't matter -- leaks sees the reference and concludes that the object might still be live.

Use the Allocations Instrument. Configure it to only track live allocations (since you don't care about objects that have been deallocated). Do some stuff with your app. Check out what Allocations knows about and explain why all those objects should stick around. You can use the data mining facilities to filter down to just your objects.

Answer 4

Circular references also won't be counted in Leaks but you can track those in Allocations. Best bet is to fire up Allocations and get to a state where you think everything should be gone (or certain objects should be). If they're hanging around go dive in to them and look at where they've been retained and sort out the proper memory ownership/releasing.

As for Allocations, there are some things that it doesn't track that can affect the overall memory. Some of the things include some CGImage backing stores, some CoreAnimation stuff and some database stuff.