This question is far outdated, as it was asked for XCode 3. Please don’t consider it useful for XCode 4+. =)
My app crashes at (seemingly) random events. So, I wanted to add NSZombieEnabled to debug my iPhone application. I cloned my target and set its Info.plist to the same as the original target and set NSZombieEnabled to YES.
Once i run the app, it crashes with a stack trace of…
#0 0x3025db0c in ___forwarding___ ()
#1 0x30239db2 in __forwarding_prep_0___ ()
#2 0x304f5105 in NSPopAutoreleasePool ()
#3 0x308ee452 in _UIApplicationHandleEvent ()
#4 0x32031425 in PurpleEventCallback ()
#5 0x30235253 in CFRunLoopRunSpecific ()
#6 0x302343c8 in CFRunLoopRunInMode ()
#7 0x308e6209 in -[UIApplication _run] ()
#8 0x308eef81 in UIApplicationMain ()
#9 0x000023ef in main (argc=1, argv=0xbffff0bc) at /Users/tomen/Documents/MIB-Sprint4/main.m:26
This only happens when NSZombieEnabled is set to YES. If it is not set, the app just runs ( and crashes at different times )
I wanted to add breakpoints like “-[_NSZombie methodSignatureForSelector:]” and others, but they get deactivated during Debugging. I tried it both ways with “Load symbols lazily” turned on and off.
I also tried to set my ~/.gdbinit file to
fb -[NSException raise]
fb -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:]
fb -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]
#define NSZombies
# this will give you help messages. Set to NO to turn them off.
set env MallocHelp=YES
# might also be set in launch arguments.
set env NSZombieEnabled=YES
set env NSDeallocateZombies=NO
set env MallocCheckHeapEach=100000
set env MallocCheckHeapStart=100000
set env MallocScribble=YES
set env MallocGuardEdges=YES
set env MallocCheckHeapAbort=1
set env CFZombie 5
fb -[_NSZombie init]
fb -[_NSZombie retainCount]
fb -[_NSZombie retain]
fb -[_NSZombie release]
fb -[_NSZombie autorelease]
fb -[_NSZombie methodSignatureForSelector:]
fb -[_NSZombie respondsToSelector:]
fb -[_NSZombie forwardInvocation:]
fb -[_NSZombie class]
fb -[_NSZombie dealloc]
fb szone_error
which yield this result in the console:
The Debugger has exited with status 0.
[Session started at 2009-09-08 13:48:40 +0200.]
Loading program into debugger…
GNU gdb 6.3.50-20050815 (Apple version gdb-966) (Tue Mar 10 02:43:13 UTC 2009)
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This GDB was configured as "i386-apple-darwin".warning: Unable to read symbols for "/System/Library/Frameworks/UIKit.framework/UIKit" (file not found).
warning: Unable to read symbols from "UIKit" (not yet mapped into memory).
warning: Unable to read symbols for "/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics" (file not found).
warning: Unable to read symbols from "CoreGraphics" (not yet mapped into memory).
Pending breakpoint 1 - "-[NSException raise]" resolved
Pending breakpoint 2 - "-[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:]" resolved
Pending breakpoint 3 - "-[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]" resolved
Pending breakpoint 14 - "szone_error" resolved
Program loaded.
sharedlibrary apply-load-rules all
Attaching to program: `/Users/tomen/Library/Application Support/iPhone Simulator/User/Applications/F77D9D82-0B34-4B8D-9076-AE883A2714F4/MIB.app/MIB', process 279.
Re-enabling shared library breakpoint 1
Re-enabling shared library breakpoint 2
Re-enabling shared library breakpoint 3
Re-enabling shared library breakpoint 14
Re-enabling shared library breakpoint 16
Re-enabling shared library breakpoint 17
Re-enabling shared library breakpoint 18
warning: Couldn't raise load state for requested objfile: "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation" for breakpoint 1/
warning: Couldn't raise load state for requested objfile: "/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation" for breakpoint 2/
warning: Couldn't raise load state for requested objfile: "/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation" for breakpoint 3/
Why do my breakpoints get deactivated?
I’ve been trying this approach as well with the same results. My understanding is that NSZombie breakpoints are no longer valid in Leopard and Snow Leopard.
Some alternatives:
1) Dump the eax register on obj_msg_send. I haven’t personally tried this one but I found many posts on the subject:
How to debug EXC_BAD_ACCESS that occurs only on release target for an iPhone app?
2) Use info malloc-history. Works nicely in the simulator but I’ve had little luck getting the logs off of the device.Finding freed deallocated instances of objects
3) Probably the best thing to do is run your app in Instruments. Note that NSZombie mode isn’t available on the device. This may be of help:
iPhone memory debug NSZombie