How to use MallocStackLogging on the device?

Question

I've a memory issue in an iPhone app that I'd like to debug with MallocStackLogging. The error involves the gyroscope so I have to debug on the device not the simulator.

I've set the MallocStackLogging environment variable and the iPhone properly records the mallock stack logs:

MyApp(1856) malloc: recording malloc stacks to disk using standard recorder MyApp(1856) malloc: stack logs being written into /private/var/mobile/Applications/1FD1F8D2-5D30-4AA7-B426-C52FE20266DE/tmp/stack-logs.1856.MyApp.index MyApp(1856) malloc: Please issue: cp /private/var/mobile/Applications/1FD1F8D2-5D30-4AA7- B426-C52FE20266DE/tmp/stack-logs.1856.MyApp.e8z3IL.link /tmp/ 

Now how can I work with them?

I can transfer them to the Mac using the Xcode Organizer. But what should I do with these two files?

• stack-logs.1856.MyApp.index
• stack-logs.1856.MyApp.e8z3IL.link

I tried moving the files in /tmp on the Mac and called:

$ malloc_history 1856 -all_events malloc_history cannot examine process 1856 because the process does not exist. 

Clearly, the malloc_history command looks for running processes on the local machine. I'm missing an option to specify the log file manually.

Is there any way to get this to work either directly working with Xcode on the (non-jailbroken) device or after transferring the logs to the Mac?

Answer 1

Here is how I debug APP with malloc stack history on idevice, it's really complicate, but I have no other way to deal with an auto release pool memory problem.

1. You need A jailbreak idevice with developer tools installed, then you have gdb.

2. To enable malloc stack loggin, you need set environment variables MallocStackLoggingNoCompact and MallocStackLogging, we need some trick to do it.

First, we need grant your app root privilege.

 mv -f /User/Application/xxxxxxxxxxxxx/YOUR_APP.app /Application/YOUR_APP.app  cd /Application  chown -R root:wheel YOUR_APP.app  chmod 4755 YOUR_APP.app/YOUR_APP 

Rename your program

mv YOUR_APP.app/YOUR_APP   YOUR_APP.app/BACK_UP_NAME 

Use a short shell scrip to start your program, so we can keep the env. Save it to YOUR_APP.app/YOUR_APP

#!/bin/bash export MallocStackLogging=1 export MallocStackLoggingNoCompact=1  exec /Applications/YOUR_APP.app/BACK_UP_NAME 

Done.

Just start you app, touching on the icon or use open command, you'll see a stack log file in /tmp directory.

Use ps aux | grep YOUR_APP find process id, gdb -p PROCESS_ID attach to the progress, make a breakpoint, try info malloc ADDRESS, malloc history will show up.