ios - 如何调试 Flutter iOS 崩溃

Question

我们从我们的 Flutter 应用程序的 Testflight 发行版中得到了一些崩溃。我们很难确定问题究竟出在哪里，因为崩溃日志并没有告诉我们太多。

这是日志( gist of full crash log/Xcode screenshot ):

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x00000003b3801090
VM Region Info: 0x3b3801090 is not in any region.  Bytes after previous region: 4622127249  
      REGION TYPE                      START - END             [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      MALLOC_NANO            0000000280000000-00000002a0000000 [512.0M] rw-/rwx SM=PRV  
--->  
      UNUSED SPACE AT END

Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [4572]
Triggered by Thread:  0

Thread 0 name:
Thread 0 Crashed:
0   libobjc.A.dylib                 0x000000018a902090 objc_msgSend + 16
1   Flutter                         0x00000001009d6f4c -[SemanticsObject hasChildren] + 60 (accessibility_bridge.mm:160)
2   Flutter                         0x00000001009d8334 -[SemanticsObject accessibilityContainer] + 36 (accessibility_bridge.mm:287)
3   UIAccessibility                 0x0000000195f88898 -[NSObject(AXPrivCategory) _accessibilityParentView] + 84 (NSObjectAccessibility.m:7787)
4   UIAccessibility                 0x0000000195f88734 -[NSObject(AXPrivCategory) _accessibilityWindow] + 92 (NSObjectAccessibility.m:7762)
5   UIAccessibility                 0x0000000195f8ff68 -[NSObject(AXPrivCategory) _accessibilityConvertSystemBoundedScreenRectToContextSpace:] + 48 (NSObjectAccessibility.m:10192)
6   UIAccessibility                 0x0000000195f83ee8 -[NSObject(AXPrivCategory) _iosAccessibilityAttributeValue:] + 4624 (NSObjectAccessibility.m:5303)
7   UIAccessibility                 0x0000000195f6637c _copyMultipleAttributeValuesCallback + 540 (UIAccessibilityRuntime.m:345)
8   AXRuntime                       0x0000000194fc56e0 ___AXXMIGCopyMultipleAttributeValues_block_invoke + 60 (AccessibilityPriv.m:1262)
9   AXRuntime                       0x0000000194fc5264 _handleNonMainThreadCallback + 60 (AccessibilityPriv.m:466)
10  AXRuntime                       0x0000000194fc5570 _AXXMIGCopyMultipleAttributeValues + 332 (AccessibilityPriv.m:1261)
11  AXRuntime                       0x0000000194fbf4b4 _XCopyMultipleAttributeValues + 392 (AccessibilityClientDefsServer.c:1354)
12  AXRuntime                       0x0000000194fd443c mshMIGPerform + 268 (MachServerHelper.c:447)
13  CoreFoundation                  0x000000018ab5d07c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 56 (CFRunLoop.c:1937)
14  CoreFoundation                  0x000000018ab5c7a8 __CFRunLoopDoSource1 + 444 (CFRunLoop.c:2075)
15  CoreFoundation                  0x000000018ab5767c __CFRunLoopRun + 2168 (CFRunLoop.c:3098)
16  CoreFoundation                  0x000000018ab56adc CFRunLoopRunSpecific + 464 (CFRunLoop.c:3192)
17  GraphicsServices                0x0000000194adc328 GSEventRunModal + 104 (GSEvent.c:2246)
18  UIKitCore                       0x000000018ec51ae0 UIApplicationMain + 1936 (UIApplication.m:4773)
19  Runner                          0x0000000100666cec main + 96 (AppDelegate.swift:5)
20  libdyld.dylib                   0x000000018a9e0360 start + 4

我们已经尝试按照本指南进一步象征日志 https://github.com/flutter/flutter/wiki/Crashes .使用这些步骤:

获取我们的 flutter 引擎修订版

为我们的 Flutter.framework 版本下载正确的 dSYM 文件

尝试用以下符号表示:

export DEVELOPER_DIR="/Applications/Xcode.app/Contents/Developer"

cp -i /Applications/Xcode.app/Contents/SharedFrameworks/DVTFoundation.framework/Versions/A/Resources/symbolicatecrash ./

symbolicatecrash 2020-01-11.crash Flutter.dSYM > symbolicated.crash

但并没有真正改善，见变化 in this gist

有关从何处开始查找导致此类崩溃的编程错误的任何提示。我们正在寻找有关调试内部 flutter 崩溃的一般技巧和这种特殊情况的技巧。

此外，我们无法重现这次崩溃，因为我们不知道去哪里寻找。

Answer 1

根据您的崩溃报告 VM Region Info: 0x3b3801090 is not in any region.崩溃可能是因为正在访问一些未分配的内存...这可能是因为 ___AXXMIGCopyMultipleAttributeValues_block_invoke正在从主线程外部调用(看起来像根据堆栈跟踪)。但是不知道能不能调试lib AXRuntime。

您是否尝试过在 xcode 中使用查看日志窗口来表示崩溃报告？ (你必须有一个物理 iphone X (iphone10)，这样架构就不会在过程中丢失......这个 page 可能会有所帮助。