I am running instruments to analyze memory leaks in my application,
but it does not show any responsible libraries for any allocations:
Neither it shows any methods/variables in stack trace, it just shows this:
Is there any setting that I am missing? It used to show earlier, it has stopped showing these just recently.
Here are a couple screen shots of how I currently have mine configured. Maybe these will help. First thing I would do is check to make sure that within the current scheme, you have your "Profile" Build Configuration set to Debug like in the first image below.
Also, have you tried right clicking on "Responsible Library" header to remove the checkmark and re-add it like in my last screenshot, to give it a virtual smack? I'll keep looking to see if I can find out anything else more helpful.
Close instruments. Make sure spotlight indexes your build artifacts. You can do this manually by running mdimport from the command line. Reopen instruments.
Obviously, make sure your derived data location, etc. is not in spotlight's blacklist. This is controlled by System Preferences.
Instruments relies on Spotlight for a lot of what it does.
1.When my app crashes and there's no message in console window Xcode shows me a green line with signature EXC_BAD_ACCESS or PROGRAM RECEIVED SIGNAL SIGABRT in the code editor. The question is: does Xcode always put this green line at the line of code where a bug is placed? If i see this green line put at the line
[myObject myMethod];
may i be confident that the bug should be searched for inside the myMethod function? Or maybe it may mean something else?
2.Sometimes this green line is put inside main.m file at the line
int retVal = UIApplicationMain(argc, argv, nil, nil);
Do you know what specific about placing the hint there? What does it mean?
3.Also sometimes the strangest thing happens: Xcode shows me a file with assembler code and the green line inside this code. Why? What should i understand when i see that?
4.If i repeatedly do the following: enter a screen, then do something, then quit the screen - my app crashes. It may crash at the second time or at the seventh one. What is the most common causes for such a crash? A memory leak? But Analyze tells me there are no leaks in my app. What do you think it may be?
As I said in another post :
In XCode, go to menu "edit scheme", choose the running configuration and add 'NSZombieEnabled' like in the picture below, when your apps crashes, it will provide you additional infos on the crash that should help you debug it.
Note that when your application debug is over, remove the NSZombieEnabled command as it impacts the application performances
The simple answer to point 4: The most common cause of a crash accessing deallocated/over-released memory.
You can check for NSZombies or debug any memory references that you can find in the error message.
You can find some hints here iPhone Xcode debugging
Regarding (3) I do not think there is a way to interpret that assembly code.
I am working on an iPhone project containing a ton of code. The application receives outside requests and performs actions. However, I cannot figure out exactly where the app begins executing code for a particular event. Is there some functionality in Xcode which would allow me to solve this problem?
Thank you.
Have you tried setting break points in your code? Click on the line numbers column in Xcode on the number to set a break point.
Without knowing more about what these requests are or where they are coming from, its hard to give any advice on what tools Xcode might have, but looking in any project files named <xxx>AppDelegate.m or <xxx>Controller.m would be a good start, placing breakpoints on likely sounding methods.
I figured out that you can use the Instruments Profiler to this end.
Start the profiler
Choose "Time Profiler"
In the bottom left section make sure the following are checked: Show Obj-C only and Hide System Libraries
In the timeline, click on the the point before the event occurred.
Click the left-most icon in "inspection range" (located on the top-bar immediately to the left of clock)
In the timeline, click on the point after the event completed. (optional)
Click the right-most icon in "inspection range"
Inspect the Call Tree.
My favorite candidate again. I am in the process of identifying memory leaks in my app (a puzzling challenge for a newbe like me).
I am using the xCode leak analyzer, but what puzzles me is how to trace back a memory leak to its variable or value. Is there a pointer to the instances that have reserved a memory address where a leak is identifyed?
How do I best go about it?
Are you aware of the Clang analyzer? Hit Cmd-Shift-A in Xcode and prepare to be pleasantly surprised. (This should run the Build → Build and Analyze command. It’s something like building the sources, but you get an analyzer log instead of the binary. Hopefully the analyzer will detect at least some of your leaks.)
The XCode leak analyzer tells you where the objects that were leaked were created, if you click the 'extended detail' tab on the right side of the toolbar at the bottom of the window. A call stack showing you which function created the object is shown on the right.
I'm programming an application in Objective-C and I'm getting this error:
MyApp(2121,0xb0185000) malloc: *** error for object 0x1068310: double free
*** set a breakpoint in malloc_error_break to debug
It is happening when I release an NSAutoreleasePool and I can't figure out what object I'm releasing twice.
How do I set his breakpoint?
Is there a way to know what is this "object 0x1068310"?
When an object is "double-freed", the most common cause is that you're (unnecessarily) releasing an autoreleased object, and it is later autoreleased when the containing autorelease pool is emptied.
I've found that the best way to track down the extra release is to use the NSZombieEnabled environment variable for the affected executable in Xcode. For a quick rundown of how to use it, check out this CocoaDev wiki page. (In addition to this page, Apple has documented some incredibly obscure yet useful tips for debugging code in Xcode, some of which have saved my bacon more than a few times. I suggest checking out this Technical Note on developer.apple.com — link jumps to the section on Cocoa's Foundation framework).
Edit: You can often track the offending object down within the Xcode debugger, but it's often much easier if you use Instruments to assist you. From Xcode, choose Run → Start With Performance Tool → Object Allocations and you should be able to trace the offending object back to where it was created. (This will work best if you're enabled zombies as discussed above.) Note: Snow Leopard adds a Zombies tool to Instruments, accessible from the Run menu as well. Might be worth the $29 alone! ;-)
There is also a related SO question here.
You'll find out what the object is when you break in the debugger. Just look up the call stack and you will find where you free it. That will tell you which object it is.
The easiest way to set the breakpoint is to:
Go to Run -> Show -> Breakpoints (ALT-Command-B)
Scroll to the bottom of the list and add the symbol malloc_error_break
I just want to add my experience in addition to the answer of Quinn Taylor.
In one of my apps, I have to parse and save data into core data objects and later on get these objects to display on the views. In fact, the app works just fine and does not crash at all, until I tried to do a stress test of navigating back and forth multiple times, tried to open multiple views as fast as possible. The app crashes with the above message.
I have tried all the methods that Quinn suggested in his answer and still failed to find out where was the exact cause.
I set NSZombieEnabled=YES, and NSStackLogging=YES, ran the command shell malloc_history to find out why, but still no luck. It always points out to where I save the data into core data objects, in fact, I have checked thousand times the over released objects there, nothing odd.
Running in Instruments with various tools(Allocations, Leaks, etc...) still did not help. Enable the Guard Malloc still got nothing.
Final rescue: I tried to come back to the views where the objects were taken from Core Data and sent a retain message to all of these objects, and took note to these changes. It solved the issue!!!
So, I found out that I failed to retain one, that's exactly the cause. Just want to share my experience so you have another rescue for your app.
Open up the debugger console by pressing Cmd+Shift+R. There, type
break malloc_error_break
to set a breakpoint at the beginning of the malloc_error_break function.
If you want to find out what object is located at address 0x1068310, you can type the following into the debugger console:
print-object 0x1068310
Of course, you have to do this while the object is still alive -- if the object has already been freed by the time you do this, then this will not work.
Please find the below steps for how to find the object which is free and crash the application.
1) Click on the "Breakpoint navigator". 2) Then click on the
"+" button which is below. 3) Add the "Symbolic
Breakpoint..." from the list. 4) Add the
"malloc_error_break" keyword on the "Symbol" option.
Or you can also refer the below GIF presentation.
For me the issue was solved by
(gdb) call (void)_CFAutoreleasePoolPrintPools()
right after the crash. The address at the top of the stack was the address of the culprit. Threw in a retain and voila.
The address given in the log message did not get me anywhere. It never showed up in any of the various Instrumets. Apparently a pointer to some internal data which had already been freed.
Adding a symbolic breakpoint in Xcode 4
Just an update to make this relevant to Xcode 4...
From the Xcode 4 User Guide:
To add a symbolic breakpoint . . .
In the bottom-left corner of the breakpoint navigator, click the Add
button.
Choose Add Symbolic Breakpoint.
Enter the symbol name in the
Symbol field.
Click Done.
This is what the malloc_error_break breakpoint looks like in the Breakpoints window in Xcode.
Need to check the boxes to make it work.
alt text http://www.martijnthe.nl/wp-content/uploads/2009/08/Afbeelding-1.png
Check your classes and look under the dealloc method. Make sure you care calling [super dealloc].
I had this exact same problem and found out I was calling [self dealloc] instead. Just not paying attention.
In Xcode, click left of the line number to set a breakpoint. Then you can launch it by doing a "Build and Debug".
It is recommended to not have object that you create be autorelease since memory is a commodity on the iPhone. Apple recommends explicitly calling release.
To find these kinds of memory and pointer problems in general, you want to run your code against a runtime memory error checker like Valgrind. This should be able to point out lots of things your code is doing wrong, beyond those that cause it to crash.
Valgrind can work on OSX (though it says it's "unsupported and incomplete and buggy"), and with a little hacking someone got it to work on iPhone SDK executables.
Even better you can try Instruments, which is part of XCode. There's a tutorial for running it here.
If malloc_error_break is not helping...
The best way to solve this error is to run instruments with the NSZombies turned on. Instruments will flag you when the Zombie is messaged and you can trace directly back to the line of code.
Snow Leopard required, what a lifesaver though!
This is usually caused by some inspector, such as safari or safari preview. Refer to post or post and question.
Remove the select of AutoMatically Show Web ...., will remove this issue.
Note, just close safari or safari preview will not remove this issue. And you have to deselect both of safari and safari preview.
If this will not do, refer to this answer or post to debug it.