Mono Boehm vs SGen GC

Question

我在以下环境中开发了一个应用程序(在我的错误中重命名为MyApplication for privacy):

• Monotouch 2.1
• MonoDevelop 2.4.2
• MacOS 10.6.8
• iOS SDK 4.3

工作正常.

现在我尝试使用MonoDevelop 2.8.8.4迁移到iOS 5.0/5.1和Monotouch 5.2.5.我的应用程序立即崩溃,出现以下错误:

堆栈跟踪:

at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <IL 0x0009f, 0xffffffff>
  at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x00042] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:29
  at MonoTouch.UIKit.UIApplication.Main (string[]) [0x00000] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:34
  at MyApplication.Application.Main (string[]) [0x00000] in /Users/MyPC/Projects/Test/MyApplication/Main.cs:19
  at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) <IL 0x00050, 0xffffffff>

本机堆栈跟踪:

0   MyApplication                            0x000908fc mono_handle_native_sigsegv + 284
1   MyApplication                            0x00005c98 mono_sigsegv_signal_handler + 248
2   libSystem.B.dylib                   0x9138145b _sigtramp + 43
3   ???                                 0xffffffff 0x0 + 4294967295
4   libobjc.A.dylib                     0x02958753 prepareForMethodLookup + 93
5   libobjc.A.dylib                     0x0294f069 lookUpMethod + 86
6   libobjc.A.dylib                     0x0294f1d6 _class_lookupMethodAndLoadCache + 40
7   libobjc.A.dylib                     0x029620e3 objc_msgSend + 87
8   UIKit                               0x01cba799 -[UIControl sendAction:to:forEvent:] + 67
9   UIKit                               0x01cbcc2b -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
10  UIKit                               0x01cbba1c -[UIControl touchesBegan:withEvent:] + 277
11  UIKit                               0x01c4ed41 -[UIWindow _sendTouchesForEvent:] + 395
12  UIKit                               0x01c2fc37 -[UIApplication sendEvent:] + 447
13  UIKit                               0x01c34f2e _UIApplicationHandleEvent + 7576
14  GraphicsServices                    0x03fa5992 PurpleEventCallback + 1550
15  CoreFoundation                      0x00df8944 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
16  CoreFoundation                      0x00d58cf7 __CFRunLoopDoSource1 + 215
17  CoreFoundation                      0x00d55f83 __CFRunLoopRun + 979
18  CoreFoundation                      0x00d55840 CFRunLoopRunSpecific + 208
19  CoreFoundation                      0x00d55761 CFRunLoopRunInMode + 97
20  GraphicsServices                    0x03fa41c4 GSEventRunModal + 217
21  GraphicsServices                    0x03fa4289 GSEventRun + 115
22  UIKit                               0x01c38c93 UIApplicationMain + 1160
23  ???                                 0x090a61fc 0x0 + 151675388
24  ???                                 0x090a60c8 0x0 + 151675080
25  ???                                 0x090a59c0 0x0 + 151673280
26  ???                                 0x090a590c 0x0 + 151673100
27  ???                                 0x090a5997 0x0 + 151673239
28  MyApplication                            0x0000a002 mono_jit_runtime_invoke + 722
29  MyApplication                            0x00169efe mono_runtime_invoke + 126
30  MyApplication                            0x0016dfe4 mono_runtime_exec_main + 420
31  MyApplication                            0x00173405 mono_runtime_run_main + 725
32  MyApplication                            0x00067205 mono_jit_exec + 149
33  MyApplication                            0x002116d5 main + 2837
34  MyApplication                            0x00003055 start + 53
35  ???                                 0x00000004 0x0 + 4

执行本机代码时获得SIGSEGV.这通常表示单声道运行时或应用程序使用的本机库之一出现致命错误.

如果我将其部署到iOS SDK 4.3,也是一样的.我想这可能是这里提到的新GC SGen的问题http://www.infoq.com/news/2012/02/MonoTouch-SGen

更新:事实上,在一个Alert节目中显示错误为lv.Message ="Copy ...";

类句柄:由于对象已被垃圾回收,因此无法完成请求的操作

我怎么能解决它？

Answer 1

在MonoTouch 4中,GC会更积极地执行,以尽早捕获某种类型的编程错误:确保GC不会早期释放本机对象.

最常见的模式是在方法中声明变量:

void Method ()
{
    var view = new UIView ();
    otherNativeObject.NativeProperty = view;
}

这里发生的是托管GC没有看到otherNativeObject有对视图的引用,所以当方法完成执行时,GC将释放视图.稍后,otherNativeObject将尝试使用该视图,最终会发生类似于您报告的崩溃的崩溃(确切的堆栈跟踪和消息将根据释放的本机对象的访问位置而有所不同).

上面例子的修复很简单,只需使视图成为一个类变量:

UIView view;
void Method ()
{
    view = new UIView ();
    otherNativeObject.NativeProperty = view;
}

现在,当方法退出时,GC将无法释放视图.

请注意,这次崩溃在MonoTouch 4中并不新鲜,使GC更具侵略性的效果是,您在调试时会看到问题,而不是在客户(非常随机)崩溃时听到它.