objc_msgSend() and EXC_BAD_ACCESS in cocoa app
Generally speaking, how do we avoid objc_msgSend() crashes in our Mac Apps? Also, how do we avoid the EXC_BAD_ACCESS crashes? Why do we get it? How can we manage these kinds of errors? They are on the increase on our app and would like to ask guidance and help on this matter.
We are using XCode 3.2.5 and our project is a Cocoa one, using Objective-C language. Our webservice is an IIS-powered ASP.Net website (from where we can download/upload an XML files and images).
We are developing a cocoa-app in Mac, and we encounter this like two times in ten tries of launching the app. This app has a sketch app, and when we run the app, it just freezes and crashes within 1 minute without doing anything. Some functions this app does is:
- download xml from web and interpret on our app
- login to a web service
- has a sketch pad
- has a timer
- drag and drop functions
- upload xml data
- download images and display on our app
The crash is not limited to the post-launch of the app. Sometimes, when manipulating the program like drag-drop, downloading dataset, and doing add/edit/delete functions on our mac app, the app crashes as well.
Honestly speaking, we are relatively new to this development platform and environment, and we are still learning. Can you guide us on this issue? Like some resources or hints on where we did it wrong? Thanks a lot and more power to everyone here.
The folowing is an example of a crash report:
Process: Sketch [63065]
Path: /Users/william_hooley_27Inch/Desktop/untitled folder/MacGlass.app/Contents/MacOS/Sketch
Identifier: com.apple.CocoaExamples.Sketch
Version: 1.049 (48.1)
Code Type: X86 (Native)
Parent Process: launchd [116]
Date/Time: 2011-04-14 13:12:15.421 +1000
OS Version: Mac OS X 10.6.5 (10H574)
Report Version: 6
Interval Since Last Report: 714907 sec
Crashes Since Last Report: 17
Per-App Interval Since Last Report: 206437 sec
Per-App Crashes Since Last Report: 5
Anonymous UUID:
086C860F-E28E-4256-84F9-9692782AAD01
Exception Type: EXC_BAD_ACCESS
(SIGBUS) Exception Codes:
KERN_PROTECTION_FAILURE at
0x0000000000000044 Crashed Thread: 0
Dispatch queue: com.apple.main-thread
Thread 0 Crashed: Dispatch queue:
com.apple.main-thread 0
com.apple.AppKit
0x91a8e6cb
_recursiveInvalidateCachedVisibleRectValue
+ 24 1 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
2 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 3 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
4 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 5 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
6 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 7 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
8 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 9 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
10 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 11 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
12 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 13 com.apple.CoreFoundation 0x995f02c0 CFArrayApplyFunction + 224
14 com.apple.AppKit
0x91a8e70d
_recursiveInvalidateCachedVisibleRectValue
+ 90 15 com.apple.AppKit 0x91a8e2e1 -[NSView _setSuperview:] +
684 16 com.apple.AppKit
0x91a8db02 -[NSView addSubview:] + 383
17 com.apple.CocoaExamples.Sketch
0x00094cbf -[viewTasksDisplay Appear:]
+ 242 18 com.apple.CocoaExamples.Sketch
0x000c2e8f -[MainWindow
ShowLeftScreen:] + 964 19
com.apple.CocoaExamples.Sketch
0x0003e301 -[viewOptionMenuItemmouseDown:] + 2055 20
com.apple.AppKit
0x91bc6c68 -[NSWindow sendEvent:] +
5549 21 com.apple.AppKit
0x91adf817 -[NSApplication sendEvent:]
+ 6431 22 com.apple.AppKit 0x91a732a7 -[NSApplication run] + 917
23 com.apple.AppKit
0x91a6b2d9 NSApplicationMain + 574 24
com.apple.CocoaExamples.Sketch
0x0001b33e main + 30 25
com.apple.CocoaExamples.Sketch
0x00001eba start + 54 Thread 1:
Dispatch queue:
com.apple.libdispatch-manager 0
libSystem.B.dylib
0x98002982 kevent + 10 1
libSystem.B.dylib
0x9800309c _dispatch_mgr_invoke + 215
2 libSystem.B.dylib
0x98002559 _dispatch_queue_invoke +
163 3 libSystem.B.dylib
0x980022fe _dispatch_worker_thread2 +
240 4 libSystem.B.dylib
0x98001d81 _pthread_wqthread + 390 5
libSystem.B.dylib
0x98001bc6 start_wqthread + 30 Thread
2: 0 libSystem.B.dylib
0x97fdc0fa mach_msg_trap + 10 1
libSystem.B.dylib
0x97fdc867 mach_msg + 68 2
com.apple.CoreFoundation
0x995f837f __CFRunLoopRun + 2079
Another crash report:
Date/Time: 2011-04-14 13:27:02
+1000 OS Version: 10.6.5 (Build 10H574) Architecture: x86_64 Report
Version: 6 Command: MacGlass
Path:
/Users/william_hooley_27Inch/Desktop/untitled
folder/MacGlass.app/Contents/MacOS/Sketch
Version: 1.050 (48.1) Parent:
launchd [116] PID: 63101
Event: hang Duration:
3.58s (sampling started after 2 seconds) Steps: 16 (100ms
sampling interval) Pageins: 0
Pageouts: 0 Process:
Sketch [63101] Path:
/Users/william_hooley_27Inch/Desktop/untitled
folder/MacGlass.app/Contents/MacOS/Sketch
UID: 501 Thread edef3d4
DispatchQueue 100 User stack:
16 start + 54 (in Sketch) [0x1f6a]
16 main + 30 (in Sketch) [0x1b3ee]
16 NSApplicationMain + 574 (in AppKit) [0x91a6b2d9]
16 -[NSApplication run] + 821 (in AppKit) [0x91a73247]
16 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:]
+ 156 (in AppKit) [0x91ab0fce]
16 _DPSNextEvent + 847 (in AppKit) [0x91ab178d]
16 BlockUntilNextEventMatchingListInMode
+ 81 (in HIToolbox) [0x95bd0bd6]
16 ReceiveNextEventCommon + 354 (in
HIToolbox) [0x95bd0d51]
16 RunCurrentEventLoopInMode + 392 (in
HIToolbox) [0x95bd0f9c]
16 CFRunLoopRunInMode + 97 (in
CoreFoundation) [0x995f7291]
16 CFRunLoopRunSpecific + 452 (in
CoreFoundation) [0x995f7464]
16 __CFRunLoopRun + 8059 (in CoreFoundation) [0x995f9adb]
16 __NSFireTimer + 141 (in Foundation) [0x972c39b0]
16 _handleWindowNeedsDisplay + 696 (in AppKit) [0x91adb28a]
16 -[NSWindow displayIfNeeded] + 204 (in AppKit) [0x91aa9d40]
16 -[NSView displayIfNeeded] + 818 (in AppKit) [0x91ae0a57]
16 -[NSView _displayRectIgnoringOpacity:isVisibleRect:rectIsVisibleRectForView:]
+ 4122 (in AppKit) [0x91b801cf]
16 CAViewEndDraw + 134 (in QuartzCore)
[0x961bd926]
16 pthread_cond_wait$UNIX2003 + 73 (in
libSystem.B.dylib) [0x9800b9f8]
16 __semwait_signal + 10 (in
libSystem.B.dylib) [0x9800a0a6]
Kernel stack:
15 semaphore_wait_continue + 0 [0x22a3dd]
1 lo_alltraps + 454 [0x2a08a6]
1 i386_astintr + 47 [0x2a9a9a]
1 ast_taken + 247 [0x219107]
1 bsd_ast + 806 [0x489088]
1 postsig + 432 [0x4861df]
1 exit1 + 449 [0x47ab28]
1 task_terminate_internal + 315
[0x22c56a]
Answer
The usual cause of something like this is over releasing objects. If you run your code with NSZombieEnabled, the console output should give you a clue as to where to look.
Alternatively, if this is a Macintosh application targeted at 10.5 or greater, you can enable garbage collection and not worry about retain and release at all.