我正在获取[_WebSafeForwarder forwardInvocation：]和崩溃报告，如下所示。无法在我的代码中重现相同的条件。我在每个webview.delegate = nil方法中添加了[webview stopLoading]和-(void)dealloc，其中UIWebview仍然存在以下崩溃。
#0. Crashed: com.apple.main-thread
0 libobjc.A.dylib 0x24deba86 objc_msgSend + 5
1 WebKitLegacy 0x29945e17 -[_WebSafeForwarder forwardInvocation:] + 190
2 CoreFoundation 0x25624f4d ___forwarding___ + 352
3 CoreFoundation 0x2554f298 _CF_forwarding_prep_0 + 24
4 CoreFoundation 0x25626664 __invoking___ + 68
5 CoreFoundation 0x2554b8bd -[NSInvocation invoke] + 292
6 WebCore 0x28d6b84b HandleDelegateSource(void*) + 90
7 CoreFoundation 0x255e39e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
8 CoreFoundation 0x255e3569 __CFRunLoopDoSources0 + 344
9 CoreFoundation 0x255e193f __CFRunLoopRun + 806
10 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
11 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
12 UIFoundation 0x29bb5837 -[NSHTMLReader _loadUsingWebKit] + 2038
13 Foundation 0x25e4e887 __NSThreadPerformPerform + 386
14 CoreFoundation 0x255e39e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
15 CoreFoundation 0x255e3569 __CFRunLoopDoSources0 + 344
16 CoreFoundation 0x255e193f __CFRunLoopRun + 806
17 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
18 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
19 GraphicsServices 0x26b4caf9 GSEventRunModal + 160
20 UIKit 0x29c68435 UIApplicationMain + 144
21 MyProjectName 0x1446e5 main (main.m:14)
22 libdispatch.dylib 0x251dc873 (Missing)
--
#0. Crashed: com.apple.main-thread
0 libobjc.A.dylib 0x24deba86 objc_msgSend + 5
1 WebKitLegacy 0x29945e17 -[_WebSafeForwarder forwardInvocation:] + 190
2 CoreFoundation 0x25624f4d ___forwarding___ + 352
3 CoreFoundation 0x2554f298 _CF_forwarding_prep_0 + 24
4 CoreFoundation 0x25626664 __invoking___ + 68
5 CoreFoundation 0x2554b8bd -[NSInvocation invoke] + 292
6 WebCore 0x28d6b84b HandleDelegateSource(void*) + 90
7 CoreFoundation 0x255e39e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
8 CoreFoundation 0x255e3569 __CFRunLoopDoSources0 + 344
9 CoreFoundation 0x255e193f __CFRunLoopRun + 806
10 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
11 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
12 UIFoundation 0x29bb5837 -[NSHTMLReader _loadUsingWebKit] + 2038
13 Foundation 0x25e4e887 __NSThreadPerformPerform + 386
14 CoreFoundation 0x255e39e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
15 CoreFoundation 0x255e3569 __CFRunLoopDoSources0 + 344
16 CoreFoundation 0x255e193f __CFRunLoopRun + 806
17 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
18 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
19 GraphicsServices 0x26b4caf9 GSEventRunModal + 160
20 UIKit 0x29c68435 UIApplicationMain + 144
21 MyProjectName 0x1446e5 main (main.m:14)
22 libdispatch.dylib 0x251dc873 (Missing)
#2. com.twitter.crashlytics.ios.MachExceptionServer
0 MyProjectName 0x157cdd CLSProcessRecordAllThreads + 1015005
1 MyProjectName 0x157cdd CLSProcessRecordAllThreads + 1015005
2 MyProjectName 0x157ef5 CLSProcessRecordAllThreads + 1015541
3 MyProjectName 0x14c52b CLSHandler + 967979
4 MyProjectName 0x148249 CLSMachExceptionServer + 950857
5 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
6 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
7 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#3. GAIThread
0 libsystem_kernel.dylib 0x2529b8a8 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x2529b6a9 mach_msg + 40
2 CoreFoundation 0x255e36ad __CFRunLoopServiceMachPort + 136
3 CoreFoundation 0x255e1a33 __CFRunLoopRun + 1050
4 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
5 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
6 Foundation 0x25d7d42d -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 268
7 Foundation 0x25dcbd75 -[NSRunLoop(NSRunLoop) run] + 80
8 MyProjectName 0x1d58c5 +[GAI threadMain:] + 1530053
9 Foundation 0x25e4e64d __NSThread__start__ + 1144
10 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
11 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
12 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#4. com.apple.NSURLConnectionLoader
0 libsystem_kernel.dylib 0x2529b8a8 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x2529b6a9 mach_msg + 40
2 CoreFoundation 0x255e36ad __CFRunLoopServiceMachPort + 136
3 CoreFoundation 0x255e1a33 __CFRunLoopRun + 1050
4 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
5 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
6 CFNetwork 0x25b85c47 +[NSURLConnection(Loader) _resourceLoadLoop:] + 486
7 Foundation 0x25e4e64d __NSThread__start__ + 1144
8 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
9 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
10 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#5. com.apple.CFSocket.private
0 libsystem_kernel.dylib 0x252afeec __select + 20
1 CoreFoundation 0x255e8b51 __CFSocketManager + 572
2 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
3 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
4 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#6. AFNetworking
0 libsystem_kernel.dylib 0x2529b8a8 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x2529b6a9 mach_msg + 40
2 CoreFoundation 0x255e36ad __CFRunLoopServiceMachPort + 136
3 CoreFoundation 0x255e1a33 __CFRunLoopRun + 1050
4 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
5 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
6 Foundation 0x25d7d42d -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 268
7 Foundation 0x25dcbd75 -[NSRunLoop(NSRunLoop) run] + 80
8 MyProjectName 0x29d30f +[AFURLConnectionOperation networkRequestThreadEntryPoint:] (AFURLConnectionOperation.m:168)
9 Foundation 0x25e4e64d __NSThread__start__ + 1144
10 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
11 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
12 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#7. WebThread
0 libsystem_kernel.dylib 0x252af998 __psynch_cvwait + 24
1 libsystem_pthread.dylib 0x253541a5 _pthread_cond_wait + 536
2 libsystem_pthread.dylib 0x253550f9 pthread_cond_timedwait + 44
3 WebCore 0x28d57f57 SendDelegateMessage(NSInvocation*) + 678
4 WebKitLegacy 0x29978265 CallFrameLoadDelegate(void (*)(), WebView*, objc_selector*, objc_object*) + 172
5 WebKitLegacy 0x29947877 WebFrameLoaderClient::dispatchDidFinishLoad() + 158
6 WebCore 0x28d290af WebCore::FrameLoader::checkLoadCompleteForThisFrame() + 382
7 WebCore 0x28d28e75 WebCore::FrameLoader::checkLoadComplete() + 280
8 WebCore 0x28d55bf1 WebCore::FrameLoader::checkCompleted() + 316
9 WebCore 0x28d5504b WebCore::FrameLoader::finishedParsing() + 102
10 WebCore 0x28d54f59 WebCore::Document::finishedParsing() + 312
11 WebCore 0x28d5270b WebCore::HTMLDocumentParser::prepareToStopParsing() + 118
12 WebCore 0x28dddbcb WebCore::HTMLDocumentParser::resumeParsingAfterYield() + 102
13 WebCore 0x28cff4a1 WebCore::ThreadTimers::sharedTimerFiredInternal() + 136
14 WebCore 0x28cff3f5 WebCore::timerFired(__CFRunLoopTimer*, void*) + 28
15 CoreFoundation 0x255e4177 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 14
16 CoreFoundation 0x255e3da9 __CFRunLoopDoTimer + 936
17 CoreFoundation 0x255e1bf5 __CFRunLoopRun + 1500
18 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
19 CoreFoundation 0x2552ffbd CFRunLoopRunInMode + 108
20 WebCore 0x28d457b7 RunWebThread(void*) + 422
21 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
22 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
23 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#8. JavaScriptCore::Marking
0 libsystem_kernel.dylib 0x252af998 __psynch_cvwait + 24
1 libsystem_pthread.dylib 0x253541a5 _pthread_cond_wait + 536
2 libsystem_pthread.dylib 0x253550b9 pthread_cond_wait + 40
3 libc++.1.dylib 0x24d7469d std::__1::condition_variable::wait(std::__1::unique_lock<std::__1::mutex>&) + 36
4 JavaScriptCore 0x2891a781 JSC::GCThread::waitForNextPhase() + 104
5 JavaScriptCore 0x2891a7ef JSC::GCThread::gcThreadMain() + 62
6 JavaScriptCore 0x287269e1 WTF::threadEntryPoint(void*) + 148
7 JavaScriptCore 0x2872693f WTF::wtfThreadEntryPoint(void*) + 14
8 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
9 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
10 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#9. NSOperationQueue 0x15e6cc20 :: NSOperation 0x15d230e0 (QOS: USER_INTERACTIVE)
0 libsystem_kernel.dylib 0x2529b8f8 semaphore_wait_trap + 8
1 libsystem_platform.dylib 0x2534f289 _os_semaphore_wait + 12
2 libdispatch.dylib 0x251bcc6d _dispatch_barrier_sync_f_slow + 372
3 MyProjectName 0x27dd8f __69-[SDWebImageManager downloadImageWithURL:options:progress:completed:]_block_invoke98 (SDWebImageManager.m:189)
4 MyProjectName 0x275e71 __72-[SDWebImageDownloader downloadImageWithURL:options:progress:completed:]_block_invoke93 (SDWebImageDownloader.m:163)
5 MyProjectName 0x27a8fb -[SDWebImageDownloaderOperation connection:didFailWithError:] (SDWebImageDownloaderOperation.m:419)
6 CFNetwork 0x25c683a1 __65-[NSURLConnectionInternal _withConnectionAndDelegate:onlyActive:]_block_invoke + 56
7 CFNetwork 0x25c68359 -[NSURLConnectionInternal _withConnectionAndDelegate:onlyActive:] + 184
8 CFNetwork 0x25c6847d -[NSURLConnectionInternal _withConnectionAndDelegate:] + 36
9 CFNetwork 0x25c44125 _NSURLConnectionDidFail(_CFURLConnection*, __CFError*, void const*) + 84
10 CFNetwork 0x25be3203 ___ZN27URLConnectionClient_Classic17_delegate_didFailEP9__CFErrorU13block_pointerFvvE_block_invoke + 86
11 CFNetwork 0x25be1a83 ___ZN27URLConnectionClient_Classic18_withDelegateAsyncEPKcU13block_pointerFvP16_CFURLConnectionPK33CFURLConnectionClientCurrent_VMaxE_block_invoke_2 + 70
12 libdispatch.dylib 0x251b3cab _dispatch_client_callout + 22
13 libdispatch.dylib 0x251bb543 _dispatch_block_invoke + 450
14 CFNetwork 0x25b13e83 RunloopBlockContext::_invoke_block(void const*, void*) + 18
15 CoreFoundation 0x2552fc09 CFArrayApplyFunction + 36
16 CFNetwork 0x25b13d6b RunloopBlockContext::perform() + 182
17 CFNetwork 0x25b13c35 MultiplexerSource::perform() + 216
18 CFNetwork 0x25b13ac9 MultiplexerSource::_perform(void*) + 48
19 CoreFoundation 0x255e39e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
20 CoreFoundation 0x255e35d7 __CFRunLoopDoSources0 + 454
21 CoreFoundation 0x255e193f __CFRunLoopRun + 806
22 CoreFoundation 0x255301c9 CFRunLoopRunSpecific + 516
23 CoreFoundation 0x25570f23 CFRunLoopRun + 98
24 MyProjectName 0x27779b -[SDWebImageDownloaderOperation start] (SDWebImageDownloaderOperation.m:117)
25 Foundation 0x25e38b0d __NSOQSchedule_f + 192
26 libdispatch.dylib 0x251bde7f _dispatch_queue_drain + 1762
27 libdispatch.dylib 0x251b6e17 _dispatch_queue_invoke + 282
28 libdispatch.dylib 0x251bf20d _dispatch_root_queue_drain + 400
29 libdispatch.dylib 0x251bf07b _dispatch_worker_thread3 + 94
30 libsystem_pthread.dylib 0x25352e0d _pthread_wqthread + 1024
31 libsystem_pthread.dylib 0x253529fc start_wqthread + 8
#10. com.apple.root.default-qos
0 libsystem_kernel.dylib 0x252af998 __psynch_cvwait + 24
1 libsystem_pthread.dylib 0x253541a5 _pthread_cond_wait + 536
2 libsystem_pthread.dylib 0x253550b9 pthread_cond_wait + 40
3 Foundation 0x25dc840f -[NSCondition wait] + 194
4 Foundation 0x25d8f40b -[NSObject(NSThreadPerformAdditions) performSelector:onThread:withObject:waitUntilDone:modes:] + 850
5 Foundation 0x25d92be1 -[NSObject(NSThreadPerformAdditions) performSelectorOnMainThread:withObject:waitUntilDone:] + 136
6 UIFoundation 0x29bb611f -[NSHTMLReader _load] + 386
7 UIFoundation 0x29bb6b21 -[NSHTMLReader attributedString] + 24
8 UIFoundation 0x29b5ac35 _NSReadAttributedStringFromURLOrData + 5304
9 UIFoundation 0x29b596f5 -[NSAttributedString(NSAttributedStringUIFoundationAdditions) initWithData:options:documentAttributes:error:] + 116
10 MyProjectName 0x19cecf -[MyStaticLibrary handleHTMLCharactersForTitle:] (MyStaticLibrary.m:3132)
11 MyProjectName 0x1a8905 __47-[MyNetworkRequest onHTTPSuccessWithResponse:]_block_invoke143 (MyNetworkRequest.m:484)
12 libdispatch.dylib 0x251b3cbf _dispatch_call_block_and_release + 10
13 libdispatch.dylib 0x251bf6a1 _dispatch_root_queue_drain + 1572
14 libdispatch.dylib 0x251bf07b _dispatch_worker_thread3 + 94
15 libsystem_pthread.dylib 0x25352e0d _pthread_wqthread + 1024
16 libsystem_pthread.dylib 0x253529fc start_wqthread + 8
#11. Thread
0 libsystem_kernel.dylib 0x252afffc __semwait_signal + 24
1 libsystem_c.dylib 0x25203bcd nanosleep + 172
2 libc++.1.dylib 0x24db38f5 std::__1::this_thread::sleep_for(std::__1::chrono::duration<long long, std::__1::ratio<1ll, 1000000000ll> > const&) + 136
3 JavaScriptCore 0x28ad9b01 bmalloc::Heap::scavenge(std::__1::unique_lock<bmalloc::StaticMutex>&, std::__1::chrono::duration<long long, std::__1::ratio<1ll, 1000ll> >) + 256
4 JavaScriptCore 0x28ad98eb bmalloc::Heap::concurrentScavenge() + 78
5 JavaScriptCore 0x28adb7b7 bmalloc::AsyncTask<bmalloc::Heap, void (bmalloc::Heap::*)()>::entryPoint() + 98
6 JavaScriptCore 0x28adb751 bmalloc::AsyncTask<bmalloc::Heap, void (bmalloc::Heap::*)()>::pthreadEntryPoint(void*) + 8
7 libsystem_pthread.dylib 0x25354c7f _pthread_body + 138
8 libsystem_pthread.dylib 0x25354bf3 _pthread_start + 110
9 libsystem_pthread.dylib 0x25352a08 thread_start + 8
#12. Thread
0 libsystem_pthread.dylib 0x253529f4 start_wqthread + 14
#13. Thread
0 libsystem_kernel.dylib 0x252b0864 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x25352e19 _pthread_wqthread + 1036
2 libsystem_pthread.dylib 0x253529fc start_wqthread + 8
#14. Thread
0 libsystem_kernel.dylib 0x252b0864 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x25352e19 _pthread_wqthread + 1036
2 libsystem_pthread.dylib 0x253529fc start_wqthread + 8
#15. PLClientLoggingFlushQueue
0 libsystem_platform.dylib 0x2534e96a _platform_memmove + 105
1 CoreFoundation 0x2553f0c7 CFStringGetBytes + 634
2 CoreFoundation 0x2553f0c7 CFStringGetBytes + 634
3 CoreFoundation 0x25677ab9 __writeObject15 + 324
4 CoreFoundation 0x2567841d __writeObject15 + 2728
5 CoreFoundation 0x2567841d __writeObject15 + 2728
6 CoreFoundation 0x2567841d __writeObject15 + 2728
7 CoreFoundation 0x2567841d __writeObject15 + 2728
8 CoreFoundation 0x2567841d __writeObject15 + 2728
9 CoreFoundation 0x256777ad __CFBinaryPlistWrite15 + 152
10 CoreFoundation 0x255729cf _CFXPCCreateXPCMessageWithCFObject + 118
11 PowerLog 0x2707ab4f -[PLClientLogger xpcSendMessage:withClientID:withKey:withPayload:] + 86
12 PowerLog 0x2707bd85 -[PLClientLogger batchTasksCacheFlush] + 500
13 libdispatch.dylib 0x251b3cbf _dispatch_call_block_and_release + 10
14 libdispatch.dylib 0x251bd3cf _dispatch_after_timer_callback + 66
15 libdispatch.dylib 0x251c65bb _dispatch_source_latch_and_call + 2042
16 libdispatch.dylib 0x251b5bff _dispatch_source_invoke + 738
17 libdispatch.dylib 0x251bd9ed _dispatch_queue_drain + 592
18 libdispatch.dylib 0x251b6e17 _dispatch_queue_invoke + 282
19 libdispatch.dylib 0x251bf20d _dispatch_root_queue_drain + 400
20 libdispatch.dylib 0x251bf07b _dispatch_worker_thread3 + 94
21 libsystem_pthread.dylib 0x25352e0d _pthread_wqthread + 1024
22 libsystem_pthread.dylib 0x253529fc start_wqthread + 8
我有同样的问题，我使用[NSAttributedString alloc] initWithData在标签上加载HTML字符串。当应用程序在后台模式和前景模式之间切换时，我的崩溃经常发生。我从Apple的文档中得到了一些提示，我认为这可能很有用。
以下是关于Apple's NSAttributedstring doc：的讨论
不应从后台线程调用HTML导入程序（即，选项字典包括NSDocumentTypeDocumentAttribute，其值为NSHTMLTextDocumentType）。它将尝试与主线程同步，失败和超时。从主线程调用它可以工作（但如果HTML包含对外部资源的引用，仍然可以超时，这应该不惜一切代价避免）。 HTML导入机制用于实现降价（即文本样式，颜色等），而不是用于常规HTML导入。