[Bug] Windows 10 and prior crashes due to missing icu.dll

[pabloleban]

Description

A game using Firebase (I'm using Firebase 13.7.0) won't work on some older versions of Windows 10 and prior due to a missing native Windows DLL called icu.dll.

I've temporarily solved this issue by including that DLL in the \Plugins\x86_64 folder, alongside the others .dlls from Firebase. Players are able to play the game with that DLL, however some Steamdeck users, which uses Linux + Proton emulation, are unable to play if I manually include icu.dll next to the other Firebase dlls. It seems that Proton doesn't like that and make the game crashes.

So I either:

• Don't include the .DLL so Steamdeck and Linux emulators users can play but old Windows users cannot play.
• Include the .DLL so old Windows can play, but the game crashes on Steamdeck and Linux emulators users.

According a user from another issue:

FirebaseCppApp 11 uses function getTimeZone in icu.dll (according Dependency Walker), that is missing on OS prior windows10.

#793 (comment)

It seems to be the case with Firebase 13.x.x

Reproducing the issue

Run a standalone IL2CPP build (not sure if it's important, but that's my case) using Firebase 13.7.0 on an outdated Windows 10 or older version.

Firebase Unity SDK Version

13.7.0

Unity editor version

6000.3.14f1

Installation Method

.unitypackage

Problematic Firebase Component(s)

Storage, Remote Config, Analytics, Crashlytics, Firestore, Functions, Authentication

Targeted Platform(s)

Desktop

Unity editor platform

Windows

Scripting Runtime

IL2CPP

Release Distribution Type

Pre-built SDK from https://firebase.google.com/download/unity

[pabloleban]

Here is the DLL I use that fixes the issue for old Windows users, but breaks the game on Linux emulators and Steamdeck.

icu.zip

[niccolo-hare]

Hi @pabloleban, thanks for reaching out. The behavior does seem similar to the issue here. Though this might be difficult to reproduce as I don't currently have a Windows machine, but based on the specific dll file, it does seem like it would cause issues with older Windows OS versions.

I think the icu.dll was included with newer Windows OS versions by default. That may be why you're only encountering issues with older Windows versions. And upon reviewing some of the details from similar posts, it looks like this can also be fixed by installing a specific Redistributable C++ version (C++ Redistributable 2015-2022). Though this would require your users to manually install this on their end.

Other than that, it's possible this might have been resolved on a more recent version of the Firebase C++ SDK. In addition, I think there have been some code migrations from C++ to C# with recent releases of the Firebase Unity SDK, which might also help resolve this. So just to double check, could you try updating your Firebase Unity SDKs to the latest version available, then see if the issue still persists?

[pabloleban]

Hey @niccolo-hare . Steam automatically installs C++ Redistributable 2015-2022 when installing the game, as it's marked as a dependency, so that's not the case here.

I will try upgrading Firebase and testing the branch with a user that I know that he had to manually add icu.dll to fix the issue and let you know if it works. Thank you.

[pabloleban]

Hey @niccolo-hare

I've an update.

I've updated to Firebase 13.12.0 and asked the user to remove the icu.dll and update the game, however the issue persists. When icu.dll was deleted, the game failed to initialize Firebase.

After including icu.dll again in the folder, the game launched successfully.

Here are the logs of the player when this issue happened.

Player-prev (8).log

According to the user, he has Windows 10 Entreprise LTSC with a Celeron B800.

Thank you.

[niccolo-hare]

Hi @pabloleban. Thanks for the confirmation, and apologies for the wait. Before I continue, I would like to note that desktop support is currently in beta, as noted here. Though I did some digging and it looks like the issue you're encountering may be expected behavior.

To clarify, per v11.2.0 of the C++ SDK, Unity applications built for Windows systems are required to link the icu.dll system library if they are using Remote Config. I believe the purpose was to add Unicode support for handling time zones in Windows systems. So adding the icu.dll file manually should resolve this issue for Windows systems prior to Windows 10.

But for systems such as the Steam Deck, you may need additional setup for Linux. I think you need to also include the equivalent .so file(s) for the icu.dll since that seems to be what Linux uses instead. I'm not quite sure which specific files are required, but I did a quick search and I think libicui18n.so and libicuuc.so are the equivalent files. Once these .so files are linked, I believe Proton should be able to handle it from there.

Let me know if you have additional questions.

[pabloleban]

Hey @niccolo-hare

The issue on Steam Deck is actually the opposite. The game works correctly under Proton when icu.dll is absent. It only crashes when I manually include icu.dll next to the Firebase DLLs.

So Linux/Proton users do not appear to be missing ICU libraries. The presence of the Windows icu.dll itself seems to be causing the crash.

At the moment I can either:

• Ship icu.dll and support older Windows versions, but break Steam Deck/Proton.
• Omit icu.dll and support Steam Deck/Proton, but older Windows versions fail to initialize Firebase.

Do you know whether Firebase officially supports bundling icu.dll for older Windows versions, or whether there is a recommended way to conditionally load it only on native Windows systems?