Android r8 Error: java.util.ConcurrentModificationException

[Pmr-precure]

Description

Hi,

After we updated to 9.0.40, we are getting this error when trying to build a release version for Android.

I happens when r8 is enabled and in our config file we keep this:

-keep class com.google.crypto.tink.** { *; } (Tbh i cant remember why we added this, but it was for sure to fix other bugs)

This prevents us from building.

If we remove this:

-keep class com.google.crypto.tink.** { *; }

Then it builds just fine. No idea why this could be to be honest.

BR.

Steps to Reproduce

1. clone repo.
2. Build a release build
3. observe error.
4. remove # -keep class com.google.crypto.tink.** { *; } in proguard.cfg.
5. delete bin and obj folder.
6. Build release version.
7. Success.

Link to public reproduction project repository

https://github.com/Pmr-precure/MauiTestProject/tree/r8_bug

Version with bug

9.0.40 SR4

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

9.0.30 SR3

Affected platforms

Android

Affected platform versions

No response

Did you find any workaround?

Only by removing -keep class com.google.crypto.tink.** { *; }

Relevant log output

[jonathanpeppers]

This kind of just looks like an internal bug in r8.jar; this is from Android and we just redistribute it:

android/src/r8/build.gradle

Line 18 in bfdfd33

implementation 'com.android.tools:r8:8.5.35'

We have a newer r8 version in .NET 10, so I wonder if the problem goes away there?

android/src/r8/build.gradle

Line 18 in ea38c0c

implementation 'com.android.tools:r8:8.7.18'

[sgjesse]

(@sgjesse from the R8 team) I have not checked the exact stack trace. but this is most likely https://issuetracker.google.com/359385828, which was fixed in R8 8.5.45 (your version is 8.5.35).

[jonathanpeppers]

@Pmr-precure as a workaround, you could download this pack:

• https://www.nuget.org/api/v2/package/Microsoft.Android.Sdk.Windows/35.99.0-preview.1.140

Unzip the r8.jar inside and put it somewhere, then set in your .csproj the path to it:

<AndroidR8JarPath>C:\path\to\r8.jar</AndroidR8JarPath>

In the meantime, we'll look into updating r8 in our next servicing release.

[Redbone8686]

#9861 (comment)