multi-view app is crashing

Question

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.

Answer 1

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.

Answer 2

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.