Fix XA_BROKEN_EXCEPTION_TRANSITIONS support #4548
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roubachof
changed the title
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I had a little more info with this try:
This stack is interesting cause we can see all the calls from the initial |
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So to sum-up, looking at this line of log: It seems that JNI is mistaking a custom user exception needed for the correctness of the result, exception which should be caught by the calling method, for a Unhandled Exception. class StopException : RuntimeException {}
class PreDrawCallback : ViewTreeObserver.IOnPreDrawListener
{
public bool OnPreDraw()
{
try
{
...
decor.Draw(blurView.mBlurringCanvas);
|=> throws StopException
|=> JNI throws an error outside of this scope;
}
catch(StopException e)
{
}
}
} |
roubachof
changed the title
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You are unfortunately encountering a "corner case" of our unhandled exception debugger integration. "Normal" .NET+IDE semantics are that exceptions are handled in "two passes":
Java exceptions don't have this two pass model, and the way we've "papered over" this difference is that when a debugger isn't attached -- the case which works for you! -- then at every managed-to-Java invocation boundary we catch every exception, then set a "pending exception" within Java which wraps the caught exception, then return to Java. This allows Java to raise the exception on its side, and allow any Java-side catch blocks to work. When a debugger is attached, we never handle exceptions at the VM boundaries, so that there can be an "unhandled exception" for the IDE to report. We had a way to way to allow apps with the debugger attached to use the non-debugger exception handling case -- which is "differently broken" in that no exceptions would ever be unhandled, because (unless you're on a new Thread) there's always a Java stack frame to return to, and thus all exceptions are in fact handled! -- but this appears to have bitrotten some time in 2015. At present, unfortunately the best I can suggest is that you not use a debugger when hitting this code path. (Printf debugging, anyone?) What we should do is fix the feature which allowed enabling "Release"-style behavior even when a debugger is attached, so that proper exception propagation can occur. What we should also do is figure out if there's a better way to improve this scenario. |
jonpryor
changed the title
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Related:
What we need to do is "reverse" the logic in What we may also want to do -- but requires further consideration -- is skip this filtering for non-Java exception types. This would cause |
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Thank you for the answer, I think I understand the issue now. I am a big fan of printf debugging, the thing is this is a visual component I'm working on (blur view for Xamarin.Forms), so it would mean that people couldn't develop their app (using hot reload...) if they are using my component... Also, even if I disregard the debugging issue, the fact that jni throws an
So if an exception occurs in the Java world, and this exception is not caught in the java world, it will create an |
In "no debugger" execution, we preserve the "normal" Java runtime semantics, not the .NET IDE Debugger "two pass exception handling" semantics.
This is where a more specific example would be handy. Imagine two implementations of C#: // C#
public class CSharpThrows : Java.Lang.IRunnable {
public void Run()
{
throw new global::System.Exception("From C#!");
}
public static void InvokeRun(Java.Lang.IRunnable r)
{
r.Run();
}
}Java: // Java
public class JavaThrows implements Runnable {
public void run() {
throw new RuntimeException("From Java!");
}
public static void callRun(Runnable r) {
r.run();
}
}If we cause an exception to be thrown from Java, called by C#: CSharpThrows.InvokeRun(new JavaThrows());
If we cause an exception to be thrown from C#, called by Java: JavaThrows.callRun(new CSharpThrows());If no debugger is attached, then All of the above is before "unhandled exceptions" enter the picture. On a "pure Java call stack", if there is an unhandled exception, As soon as there is a managed stack frame on the call stack, behavior depends upon whether or not a debugger is attached. If a C# method throws an exception or at a managed::Java stack frame boundary when the Java method throws an exception -- and the Java exception is "handled" (cleared), marshaled, and raised in managed code -- then: When a debugger is attached, Mono will look for a managed method which handles the thrown exception. Whether or not such a handler is found, a "first chance exception" dialog will be shown in the IDE. If execution continues, then Mono will execute the handler found during the first pass, if any. If no handler was found, then When no debugger is attached, all JNI boundaries are considered to catch all exceptions. If a Java::managed transition is in the call stack, the exception will be caught in C#, marshaled, and raised in Java. Java will then have a chance to execute |
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We also ran into a similar issue with the following code. This code worked in VS 16.5.5. But once we upgraded to VS 16.6.x, it stopped working. The RuntimeException thrown in ExitMessagePump() would cause the application to crash in the debug mode. I tried 16.7.1 and16.8.0 Preview 1.0, but neither of them worked in the debug mode. Do you think you will fix this issue in VS 16.8? Thanks! |
NOTE: the SIGSEGV only happens while debugging.
If in RELEASE or ran in DEBUG mode without debugging, an UNHANDLED EXCEPTION is raised, but the app doesn't crash.
I am here trying to create blur views for
Xamarin.Forms, for the android implementation I chose https://github.com/mmin18/RealtimeBlurView.I translated in C# all the classes, you can find them here:
https://github.com/roubachof/Sharpnado.Presentation.Forms/tree/secret/Sharpnado.Presentation.Forms.Droid/Renderers/MaterialFrame/RealtimeBlurView
In his java implementation, mmin18 has the following code:
https://github.com/mmin18/RealtimeBlurView/blob/master/library/src/com/github/mmin18/widget/RealtimeBlurView.java#L259-L267
For stoping the drawing process he throws a custom "STOP_EXCEPTION" in the
Drawmethod of the blur view:https://github.com/mmin18/RealtimeBlurView/blob/master/library/src/com/github/mmin18/widget/RealtimeBlurView.java#L321-L330
Remark: you have to interrupt the drawing of all the next children, so returning in the blur view's Draw method is not enough....
It seems to be fine in plain android since I couldn't find an issue talking about SIGSEGV and STOP_EXCEPTION in the original repo.
But in Xamarin.Android I get a sig segv exception:
Steps to Reproduce
Expected Behavior
No SIGSEV should be raised
Actual Behavior
Version Information
Microsoft Visual Studio Community 2019
Version 16.5.2
VisualStudio.16.Release/16.5.2+29926.136
Microsoft .NET Framework
Version 4.8.03752
Installed Version: Community
Visual C++ 2019 00435-60000-00000-AA963
Microsoft Visual C++ 2019
ASP.NET and Web Tools 2019 16.5.236.49856
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ASP.NET Web Frameworks and Tools 2019 16.5.236.49856
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Azure App Service Tools v3.0.0 16.5.236.49856
Azure App Service Tools v3.0.0
Azure Functions and Web Jobs Tools 16.5.236.49856
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Xamarin.Android SDK 10.2.0.100 (d16-5/988c811)
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Mono: c0c5c78
Java.Interop: xamarin/java.interop/d16-5@fc18c54
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SQLite: xamarin/sqlite@46204c4
Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-5@9f4ed4b
Xamarin.iOS and Xamarin.Mac SDK 13.16.0.11 (aa73e41)
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