[docs] Document how to debug JNI Object Reference crashes #7362
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jonpryor
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| `logcat-parse` combines an API around the JNI Global Reference logs with a C# REPL. | ||
| It is included with Classic Xamarin.Android installs. |
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Do we need to file an issue to distribute this as a .NET global tool? On NuGet.org? Then you could do dotnet tool install --global logcat-parse.
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Yes, I should do that.
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Might also take the opportunity to rename logcat-parse, since I don't think it's parsing logcat? 😁
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It can parse adb logcat output.
I'm open to alternative names. objref-parse?
| In particular, `adb logcat` has a `MissingMethodException` mentioning that a constructor | ||
| with the signature `(IntPtr, JniHandleOwnership)` could not be found. | ||
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| If you see a `NotSupportedException` which with |
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| Enable JNI Global Reference log collection by setting the `debug.mono.log` system property to a value which contains `gref`: | ||
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| adb shell setprop debug.mono.log gref |
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I'd suggest adding
adb logcat -G 16Mto increase the logcat buffer size, otherwise the logcat daemon will truncate messages
| Once your app crashes, `log.txt` will contain the JNI Object Reference logs. | ||
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| *However*, the output *may* be incomplete. It is not unusual for information to be missing, because *so much* | ||
| data is written to `adb logcat`. |
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We should find out what's the maximum admissible logcat buffer size and suggest setting it here
| /* 31 */ at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState) in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/obj/Release/net6.0/android-31/mcw/Android.App.Activity.cs:line 2781 | ||
| /* 32 */ at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V(_JniMarshal_PPL_V callback, IntPtr jnienv, IntPtr klazz, IntPtr p0) in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/Android.Runtime/JNINativeWrapper.g.cs:line 121 | ||
| ``` | ||
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I'd "simplify" the format here - use 1. for line numbers, the asterisks introduce visual noise IMO
| csharp> var r = grefs.AllocatedPeers.Where(p => p.KeyHandle=="0x466b26f"); | ||
| csharp> r; | ||
| { PeerInfo(State='Collected' JniType='mono/java/lang/Runnable' McwType='Java.Lang.Runnable' KeyHandle=0x466b26f Handles=1) } | ||
| ``` |
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Can we count on people having Mono installed?
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If they're on macOS, yes. Classic Xamarin.Android SDK requires msbuild, which is part of Mono.framework.
We need a better solution for "pure .NET" environments; we likely need to turn logcat-parse into a dotnet global tool.
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That's what I was thining, it should be a dotnet tool most likely. Not necessarily dotnet global one, enough that it is shipped with XA and can be invoked with just logcat-parse
| # run the app… | ||
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| adb shell run-as @PACKAGE-NAME@ cat files/.__override__/grefs.txt > grefs.txt | ||
| adb shell run-as @PACKAGE-NAME@ cat files/.__override__/lrefs.txt > lrefs.txt |
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Perhaps explain where @PACKAGE-NAME@ can be looked up? I wouldn't be surprised if many people wouldn't know what their package name actually is, it being hidden behind properties in the project file
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| If you see a `NotSupportedException` with | ||
| [*anything else* as the inner exception](https://github.com/xamarin/xamarin-android/issues/7324), | ||
| then this is *not* due to JNI object references, and the rest of this guide will not help you. |
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A suggestion to some "next step(s)" if this guide does not help might be useful, even if it says something like "The exception message should tell you what the real error is".
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* main: [docs] Document how to debug JNI Object Reference crashes (dotnet#7362) [Mono.Android] Parse cookies on redirect in AndroidClientHandler (dotnet#7373) Bump to xamarin/Java.Interop/main@fcc33ce2 (dotnet#7380) Bump to dotnet/installer@11f6b8f 7.0.100-rc.2.22459.2 (dotnet#7367) LEGO: Merge pull request 7385 Bump to xamarin/monodroid@135be73 (dotnet#7384) Bump to xamarin/xamarin-android-tools/main@0be567a9 (dotnet#7383) Bump to Tessil/robin-map@784245b4 [v1.0.1] (dotnet#7382) Bump to mono/mono@a96bde97 (dotnet#7372) [ci] Fix test categories for emu smoke tests (dotnet#7374) Bump to xamarin/monodroid@43583d02 (dotnet#7370)
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Context: dotnet/java-interop#1039