some objc_release crash. What can be a cause? - objective-c

Question

I can't reproduce some bug that happens sometimes. This is a report:
Exception Type: EXC_CRASH (SIGSEGV)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Triggered by Thread: 1
Thread 0:
0 libobjc.A.dylib 0x3b4b97fa objc_release + 10
1 MyApp 0x00173610 -[AFHTTPRequestOperation error] (AFHTTPRequestOperation.m:136)
2 MyApp 0x001460ea -[RKObjectRequestOperationLogger HTTPOperationDidFinish:] (RKObjectRequestOperation.m:209)
3 CoreFoundation 0x31121e6e __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 10
4 CoreFoundation 0x31095aac _CFXNotificationPost + 1716
5 Foundation 0x31a7bec0 -[NSNotificationCenter postNotificationName:object:userInfo:] + 68
6 Foundation 0x31a807c2 -[NSNotificationCenter postNotificationName:object:] + 26
7 MyApp 0x0017e44e __34-[AFURLConnectionOperation finish]_block_invoke (AFURLConnectionOperation.m:558)
8 libdispatch.dylib 0x3b9a10c0 _dispatch_call_block_and_release + 8
9 libdispatch.dylib 0x3b9a10ac _dispatch_client_callout + 20
10 libdispatch.dylib 0x3b9a39a4 _dispatch_main_queue_callback_4CF + 264
11 CoreFoundation 0x3112a5ac __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 4
12 CoreFoundation 0x31128e78 __CFRunLoopRun + 1304
13 CoreFoundation 0x3109346c CFRunLoopRunSpecific + 520
14 CoreFoundation 0x3109324e CFRunLoopRunInMode + 102
15 GraphicsServices 0x35dcd2e6 GSEventRunModal + 134
16 UIKit 0x33948840 UIApplicationMain + 1132
17 MyApp 0x00014d54 main (main.m:16)
18 libdyld.dylib 0x3b9b5ab4 start + 0
Thread 1 Crashed:
0 libsystem_kernel.dylib 0x3ba59838 kevent64 + 24
1 libdispatch.dylib 0x3b9a80d0 _dispatch_mgr_invoke + 228
2 libdispatch.dylib 0x3b9a261e _dispatch_mgr_thread + 34
What can i understand from such a record? Who can be a culprit?
AFHTTPRequestOperation.m:136 don't looks that can to cause the crash
135: - (NSError *)error {
136: if (!self.HTTPError && self.response) {
137: if (![self hasAcceptableStatusCode] || ![self hasAcceptableContentType]) {
so from where objc_release can come? Does objc_release means that ARC tries to release something from memory? In what period of time (place in code) it can be happened?
providing code of AFURLConnectionOperation.m :
- (void)finish {
self.state = AFOperationFinishedState;
dispatch_async(dispatch_get_main_queue(), ^{
558: [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingOperationDidFinishNotification object:self];
});
}

Answer 1

Try using the weakSelf code pattern with the block. A weak rather than a strong reference within the block will avoid the release, hopefully.
See the answers here:
What is the proper way to avoid Retain Cycle while using blocks
I actually like the 2nd most popular answer for async. And I really really like it because you have this method called "finish" -- if you happen to make self go away simultaneous with the block being executed, perhaps you get this error.
Hope that works for you.