Bug 23375 - Inexplicable null pointer errors upon upgrading to Xamarin.iOS 8 and XCode 6
Summary: Inexplicable null pointer errors upon upgrading to Xamarin.iOS 8 and XCode 6
Status: RESOLVED INVALID
Alias: None
Product: iOS
Classification: Xamarin
Component: XI runtime ()
Version: XI 8.0.0
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Zoltan Varga
URL:
Depends on:
Blocks:
 
Reported: 2014-09-25 11:55 UTC by Gabe Johnson
Modified: 2014-09-26 12:43 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED INVALID

Comment 2 Gabe Johnson 2014-09-25 12:42:44 UTC
Submitting bug report at Rolf's request from this forum discussion: http://forums.xamarin.com/discussion/comment/78210

The problem presented itself upon upgrading to Xamarin.iOS 8 and Xcode 6. It builds just fine, but when I run it on an iOS 8 simulator, it gives the following stacktrace:

2014-09-25 10:33:29.278 SimiiOS[19692:526074] System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object
  at System.String.memcpy4 (System.Byte* dest, System.Byte* src, Int32 size) [0x00005] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:3044 
  at System.String.memcpy (System.Byte* dest, System.Byte* src, Int32 size) [0x0008e] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:3136 
  at Simi.Core.iOS.Utilities.CoordinatesExtensions.PreDrawSetup (Simi.Core.iOS.Events.Rendering.PreFrameDrawEvent ev) [0x00007] in /Users/johnsogg/tmp/simi-for-xamarin/Code/SIMI/Simi.Core.iOS/Utilities/Coordinates.cs:110 
  at Simi.Core.iOS.Utilities.CoordinatesExtensions.RegisterHandlers () [0x00029] in /Users/johnsogg/tmp/simi-for-xamarin/Code/SIMI/Simi.Core.iOS/Utilities/Coordinates.cs:71 
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00044] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:230 
  --- End of inner exception stack trace ---
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x0005c] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:238 
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/MethodBase.cs:114 
  at Simi.Core.iOS.Utilities.Binding.DelayedInvokeHelper.Invoke (DelayInvokeOrder invokeOrder) [0x00054] in /Users/johnsogg/tmp/simi-for-xamarin/Code/SIMI/Simi.Core.iOS/Utilities/Binding/DelayedInvoke.cs:43 
  at Simi.iOS.AppDelegate.FinishedLaunching (MonoTouch.UIKit.UIApplication app, MonoTouch.Foundation.NSDictionary options) [0x000be] in /Users/johnsogg/tmp/simi-for-xamarin/Code/SIMI/Simi.iOS/AppDelegate.cs:62 
  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, IntPtr principal, IntPtr delegate) [0x00005] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:62 
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:46 
  at Simi.iOS.Application.Main (System.String[] args) [0x00009] in /Users/johnsogg/tmp/simi-for-xamarin/Code/SIMI/Simi.iOS/Main.cs:15 

My offending code (Coordinates.cs:110) has not changed for over a year. That line of code is simply copying variables (involving OpenTK Matrix objects). It has nothing to do with String, which is where the native exception is coming from.
Comment 3 Rolf Bjarne Kvinge [MSFT] 2014-09-25 16:36:41 UTC
Zoltan, this looks JIT-related, can you have a look?

I can reproduce it with monotouch/master, but only if the app was built using Xcode 6.0.1, it does not crash with Xcode 5.1.1.
Comment 5 Zoltan Varga 2014-09-25 19:08:03 UTC
The problem seems to be that Globals.Renderer is null in that method.
Comment 6 Rolf Bjarne Kvinge [MSFT] 2014-09-26 06:53:29 UTC
@Gabe, I get the same results, it looks like iOS doesn't invoke methods in the same order as before, causing Globals.Rendered to not become initialized when that crashing function is called.
Comment 7 Gabe Johnson 2014-09-26 10:28:01 UTC
Thanks. After Zoltan pointed out it was null, that was my first thought. I'll have to change the way things are initialized. I appreciate the extra eyes.
Comment 8 Gabe Johnson 2014-09-26 12:43:47 UTC
Even though my particular problem has been worked around, I still think you should address the mismatch between the actual error and the error message produced. The stacktrace indicates a problem deep down in a native library somewhere.

At any rate, thanks for the help!