objective-c - 一些 objc_release 崩溃。可能是什么原因？

Question

我无法重现有时会发生的一些错误。这是一份报告:

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

从这样的记录中我能理解什么？谁可能是罪魁祸首？ AFHTTPRequestOperation.m:136 看起来不会导致崩溃

135:    - (NSError *)error {
136:        if (!self.HTTPError && self.response) {
137:            if (![self hasAcceptableStatusCode] || ![self hasAcceptableContentType]) {

那么 objc_release 可以从哪里来呢？ objc_release 是否意味着 ARC 尝试从内存中释放某些内容？它会在什么时间段(代码中的位置)发生？

提供AFURLConnectionOperation.m的代码:

    - (void)finish {
        self.state = AFOperationFinishedState;

        dispatch_async(dispatch_get_main_queue(), ^{
558:            [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingOperationDidFinishNotification object:self];
        });
    }

Answer 1

尝试在 block 中使用weakSelf代码模式。 block 内的弱引用而不是强引用有望避免释放。

在这里查看答案: What is the proper way to avoid Retain Cycle while using blocks

我实际上喜欢异步的第二个最流行的答案。我真的很喜欢它，因为你有一个名为“finish”的方法——如果你碰巧在执行 block 的同时让 self 消失，也许你会得到这个错误。

希望这对您有用。