Changing timezone crashes app

[rgroenewoudt]

Android application type

.NET Android (net7.0-android, etc.)

Affected platform version

VS2022 17.5.4, .NET 7 Android

Description

When building an app with PublishTrimmed enabled, changing the device timezone crashes the app:

[monodroid] Unable to find Android.Runtime.AndroidEnvironment.NotifyTimeZoneChanged()!

illinker seems to remove the method.

The timezone is often automatically changed by getting close to an other country, even though the time itself doesn't change. (changes to Europe/Amsterdam to Europe/Berlin)

The timezone can also be changed manually in the Android settings for the same effect.

Steps to Reproduce

Attached is a new Android 7 app with PublishTrimmed enabled in debug mode which shows the started timestamp in UI.

AndroidApp1.zip

Start the app from Visual Studio in debug mode and note the time. Go to Android settings and change the current timezone to for example Afghanistan.
The app immediately crashes, VS stops debugging and the log shows the error message that AndroidEnvironment.NotifyTimeZoneChanged() is missing.

This happens in both emulator-33 and physical devices.

Did you find any workaround?

Add a linker description file containing:

<linker>
	<assembly fullname="Mono.Android">
		<type fullname="Android.Runtime.AndroidEnvironment">
			<method name="NotifyTimeZoneChanged" /> <!-- Workaround for Xamarin bug trimming method away -->
		</type>
	</assembly>
</linker>

To prevent the method being trimmed away.

Relevant log output

No response

[rgroenewoudt]

I would also like to add that this was very difficult to debug.
The message [monodroid] Unable to find Android.Runtime.AndroidEnvironment.NotifyTimeZoneChanged()! only shows up in debug mode and not in release mode.
Nothing in adb logcat or adb bugreports.

Android's ActivityManager.GetHistoricalProcessExitReasons() only reports REASON_EXIT_SELF with signal 13. (it's not recognized as crash?)

If the app is immediately killed/aborted, I would at least expect the related error message to be present in logcat.

[grendello]

@rgroenewoudt The message is logged with the ANDROID_LOG_FATAL priority, can't get any higher alas. If it was missing from the logcat, then that's on Android I'm afraid.

[grendello]

Android's ActivityManager.GetHistoricalProcessExitReasons() only reports REASON_EXIT_SELF with signal 13. (it's not recognized as crash?)

Back in the day, calling exit() from the application would actually terminate the process. At some point Android changed the behavior and right now it mostly restarts the application if exit() is called. To quit the app, one needs to call abort() now. Until very recently, we weren't consistent in that, preserving a lot of older code that still called exit() on fatal failures.

[jonathanpeppers]

@grendello do we need to do an audit of all mono_class_get_method_from_name calls and make sure we have xml to preserve it? Some might be fine to trim away, if we don't have to abort in those cases.

I will work on fixing this specific case -- adding a test. I think I can probably just try calling the method from System.Reflection in Release mode to assert that it exists.

[grendello]

@jonathanpeppers Isn't it a bug in the linker though? I was under impression that such lines preserve the entire type? If not, then what's the point of the <type> element?

[grendello]

@grendello do we need to do an audit of all mono_class_get_method_from_name calls and make sure we have xml to preserve it? Some might be fine to trim away, if we don't have to abort in those cases.

If the <type> element doesn't preserve the entire type, then yes, we probably need to list each method in the preserve lists.

[jonathanpeppers]

No, the problem here is we removed <type fullname="Android.Runtime.AndroidEnvironment" />: 11f0e1b

We don't actually have anything preserving AndroidEnvironment.NotifyTimeZoneChanged(), if it isn't called from managed code the linker doesn't know about it.

[rgroenewoudt]

If only the .NET 5+ is supported, it might also be an idea to use DynamicallyAccessedMembersAttribute.

[jonathanpeppers]

DynamicallyAccessedMembersAttribute would be good if using some type required this method, but I think all apps actually require it?