[1.18.1~ Latest] Forge is not compatible with Openj9 17

[zkitefly]

Minecraft Version: 1.18.1~Latest

Forge Version: 39.1.1~Latest :(

Steps to reproduce:

Start from openj9 17 because 1.18 onwards is java17 start
Crash
Problem description: You are trying to run with an unsupported Java Virtual Machine: Eclipse OpenJ9 VM.
Please visit https://adoptopenjdk.net and install the HotSpot variant.
OpenJ9 is not compatible with several of the conversion behaviors we rely on to run.

I don't know if OpenJ9 is supported by NeoForge, but it's very likely that it's not.

Here's some player feedback that was previously dismissed MinecraftForge/MinecraftForge#9408

Solutions for other loaders: e.g. fabric FabricMC/fabric#1019

CaffeineMC/lithium#111

Finally, I don't want NeoForge to make the same mistake, please support openj9, thanks to all the developers!

[zkitefly]

If this resolves please re-migrate back to the affected version

[TheCurle]

I can not speak for the current state of OJ9, but historically, it has not been fully compliant with the JVM spec for classloading behaviour - which means it's a non-standard, arbitrary and moving target, with no hard-and-fast specification for us to be able to know how it behaves and whether it's consistently reliable in the real world.

It was far more effort to be compatible with than our team is ever going to be capable of, and the only way we can ever be compatible with OpenJ9 is if OpenJ9 becomes fully compatible with the JVM classloading spec, which will require a lot of investigation and verification to be sure of, something we also lack the manpower for right now, given the history of OpenJ9 not really caring about breaking spec unless it really affects a major use case.

Basically, "don't make the same mistake, add support for OpenJ9" is incredibly disingenuous. It should be "don't use a JVM that doesn't follow the specifications for JVM behaviour that most systems rely on".

[TheCurle]

To clarify: If it's compatible now, we'll remove the crash check.

That's a big if.

[zkitefly]

Why attempts to use openj9 in 1.18.1 in 39.1.0 are expected, but fail in higher versions such as 39.1.1, seems very suspicious to me

Similarly, some earlier versions such as 1.7.10 1.12.2 openj9 also work fine.

I don't know if this https://github.com/eclipse-openj9/openj9openj9 repository will help at all with the current problem, but obviously I'm not a developer.

At the end of the day, thank you to anyone who contributed in any way to this project.

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为什么在1.18.1的39.1.0中 尝试使用openj9 是在预料之中 而在更高的版本 如 39.1.1 就便是失败了 我觉得这非常可疑

同样的 在一些 早期的版本中如1.7.10 1.12.2 openj9也是正常运行起来

我虽然不知道 这个 https://github.com/eclipse-openj9/openj9openj9 的仓库 会不会对当前的问题 有一点帮助 但显然 我不是一个开发者

在最后 谢谢为这个项目做出任何贡献的人

[lukebemish]

This should in theory be resolved by McModLauncher/modlauncher#114. Having tested in production (after some manual version JSON changes to bump to a modlauncher after that change) with 1.20.1 neoforge, the game launches and runs fine with OpenJ9, though I have not extensively tested for any weird edge cases that might come up.

[3TUSK]

Why attempts to use openj9 in 1.18.1 in 39.1.0 are expected, but fail in higher versions such as 39.1.1, seems very suspicious to me

Because some newer OpenJ9 distribution does not have OpenJ9 in java.vendor system property, breaking the old way of OpenJ9 detection, coincidentally proving that modlauncher has already been working fine with OpenJ9 VM.

See McModLauncher/modlauncher#67, McModLauncher/modlauncher#96 for more reference.

Also worth mentioning MinecraftForge/typetools#3.

[TheCurle]

The OpenJ9 check has been removed and seems to work fine, closing.

[Matyrobbrt]

This was not actually fixed as ModLauncher wasn't bumped to 10.1 on either branch (latest 10.1 now containing breaking changes)

[shanoaice]

Maybe a backport to 10.0 is possible? Looks like the commit on ModLauncher only change a few lines of code.

[shanoaice]

Is this still being worked on? 1.20.4 still doesn't seem to support OpenJ9.

[lukebemish]

I believe it was just waiting on modlauncher to be bumped, which is a breaking change, so I theory it should work in 1.20.5 if that got bumped?

[Matyrobbrt]

ModLauncher was bumped in 1.20.6.