理論文章

crash分析攻略：https://mp.weixin.qq.com/s/hVj-j61Br3dox37SN79fDQ

常見崩潰原因分析

分享一些常見的崩潰原因

總覽

可以通過Exception Information和Backtrace迅速判斷出大致崩潰原因。

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有些常見的崩潰都有額外的診斷信息，這些信息能夠幫助我們進(jìn)一步排查出問題。

Swift Runtime Error

Swift通過內(nèi)存安全技術(shù)來提前捕獲代碼問題。Swift Runtime Error會有比較鮮明的特征

Exception Type:  EXC_BREAKPOINT (SIGTRAP)
...
Termination Signal: Trace/BPT trap: 5
Termination Reason: Namespace SIGNAL, Code 0x5

在英特爾處理器上，崩潰信如下

Exception Type:        EXC_BAD_INSTRUCTION (SIGILL)
...
Exception Note:        EXC_CORPSE_NOTIFY
Termination Signal:    Illegal instruction: 4
Termination Reason:    Namespace SIGNAL, Code 0x4

在堆棧區(qū)域也有相關(guān)信息

Thread 0 Crashed:
0   MyCoolApp                         0x0000000100a71a88 @objc ViewController.viewDidLoad() (in MyCoolApp) (ViewController.swift:18)

如何定位解決swift runtime error

Language Exception（OC崩潰）

Apple的系統(tǒng)框架在發(fā)生runtime錯誤的時候會拋出Language Exception，比如數(shù)組越界等。會有如下特征：

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY

同時此類崩潰還有Last Exception Backtrace

Last Exception Backtrace:
0   CoreFoundation                    0x19aae2a48 __exceptionPreprocess + 220
1   libobjc.A.dylib                   0x19a809fa4 objc_exception_throw + 55

如何定位解決Language Exception

watch dog強(qiáng)殺
被watchdog強(qiáng)殺一般崩潰類型是SIGKILL，同時Termination Reason里面的Code固定為0x8badf00d。

Exception Type:  EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY
Termination Reason: Namespace SPRINGBOARD, Code 0x8badf00d

如果watchdog強(qiáng)殺是因?yàn)閍pp長時間沒有響應(yīng)，則可能會有額外信息。

Termination Description: SPRINGBOARD, 
    scene-create watchdog transgression: application<com.example.MyCoolApp>:667
    exhausted real (wall clock) time allowance of 19.97 seconds 
    | ProcessVisibility: Foreground 
    | ProcessState: Running 
    | WatchdogEvent: scene-create 
    | WatchdogVisibility: Foreground 
    | WatchdogCPUStatistics: ( 
    |  "Elapsed total CPU time (seconds): 15.290 (user 15.290, system 0.000), 28% CPU", 
    |  "Elapsed application CPU time (seconds): 0.367, 1% CPU" 
    | )

如何定位解決watchdog強(qiáng)殺

訪問僵尸對象導(dǎo)致的崩潰
訪問僵尸對象的，意思是說給已經(jīng)dealloc的對象發(fā)送消息。給已經(jīng)析構(gòu)的對象發(fā)送消息會發(fā)生 objc_msgSend, objc_retain, or objc_release類似這種崩潰。

Thread 0 Crashed:
0   libobjc.A.dylib                   0x00000001a186d190 objc_msgSend + 16
1   Foundation                        0x00000001a1f31238 __NSThreadPerformPerform + 232
2   CoreFoundation                    0x00000001a1ac67e0 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24

另外一種情況也可能代表是訪問了僵尸對象，這時候會有Last Exception Backtrace信息

Last Exception Backtrace:
0   CoreFoundation                    0x1bf596a48 __exceptionPreprocess + 220
1   libobjc.A.dylib                   0x1bf2bdfa4 objc_exception_throw + 55
2   CoreFoundation                    0x1bf49a5a8 -[NSObject+ 193960 (NSObject) doesNotRecognizeSelector:] + 139

如何定位解決訪問僵尸對象問題

Memory Access野指針問題

野指針異常類型一般是EXC_BAD_ACCESS，同時還就會有VM Region Info信息。

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000000
VM Region Info: 0 is not in any region.  Bytes before following region: 4307009536
      REGION TYPE                      START - END             [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      UNUSED SPACE AT START
--->  
      __TEXT                 0000000100b7c000-0000000100b84000 [   32K] r-x/r-x SM=COW  ...pp/MyGreatApp

如何定位解決野指針問題

Framework丟失
如果app運(yùn)行時發(fā)現(xiàn)缺少framework，會拋出 EXC_CRASH (SIGABRT)異常錯誤碼，而且你也會收到Termination Description中斷描述。

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Termination Description: DYLD, dependent dylib '@rpath/MyFramework.framework/MyFramework' 
    not found for '<path>/MyCoolApp.app/MyCoolApp', tried but didn't find: 
    '/usr/lib/swift/MyFramework.framework/MyFramework' 
    '<path>/MyCoolApp.app/Frameworks/MyFramework.framework/MyFramework' 
    '@rpath/MyFramework.framework/MyFramework' 
    '/System/Library/Frameworks/MyFramework.framework/MyFramework'