Task runClient unable to launch in OpenJDK 8 for ForgeGradle 2.3

[milandamen]

There has been an update to OpenJDK 8 Java that breaks the launch of minecraft with the runClient gradle task. In GradleStart there is a hackNatives function that hacks the Java library path to include Minecraft's native libraries. This code depends on inner workings of how Java loads native libraries. This behavior has recently changed to only load library paths on JVM startup.

How it used to work:

1. GradleStart sets sys_paths to null and adds the minecraft natives directory to java.library.path property at start of the task.
2. Minecraft boots and tries to load the awt system library.
3. The java ClassLoader checks if sys_paths is null, which is true, and then re-initializes the library paths.
4. Library awt is loaded normally and boot continues.

Behavior after Java update:

1. GradleStart sets sys_paths to null and adds the minecraft natives directory to java.library.path property at start of the task.
2. Minecraft boots and tries to load the awt system library.
3. The java ClassLoader does not check if sys_paths is null, and crashes with a NullPointerException.

Exception log:

[17:01:09] [main/ERROR] [LaunchWrapper]: Unable to launch
java.lang.reflect.InvocationTargetException: null
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_242]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_242]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_242]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_242]
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_242]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_242]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_242]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_242]
	at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:97) [start/:?]
	at GradleStart.main(GradleStart.java:25) [start/:?]
Caused by: java.lang.ExceptionInInitializerError
	at org.lwjgl.LinuxSysImplementation.<clinit>(LinuxSysImplementation.java:50) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at org.lwjgl.Sys.createImplementation(Sys.java:131) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at org.lwjgl.Sys.<clinit>(Sys.java:116) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at net.minecraft.client.Minecraft.getSystemTime(Minecraft.java:3159) ~[Minecraft.class:?]
	at net.minecraft.client.main.Main.main(Main.java:42) ~[Main.class:?]
	... 12 more
Caused by: java.lang.NullPointerException
	at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1847) ~[?:1.8.0_242]
	at java.lang.Runtime.loadLibrary0(Runtime.java:871) ~[?:1.8.0_242]
	at java.lang.System.loadLibrary(System.java:1124) ~[?:1.8.0_242]
	at java.awt.Toolkit$3.run(Toolkit.java:1636) ~[?:1.8.0_242]
	at java.awt.Toolkit$3.run(Toolkit.java:1634) ~[?:1.8.0_242]
	at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_242]
	at java.awt.Toolkit.loadLibraries(Toolkit.java:1633) ~[?:1.8.0_242]
	at java.awt.Toolkit.<clinit>(Toolkit.java:1670) ~[?:1.8.0_242]
Exception in thread "main" 	at org.lwjgl.LinuxSysImplementation.<clinit>(LinuxSysImplementation.java:50) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at org.lwjgl.Sys.createImplementation(Sys.java:131) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at org.lwjgl.Sys.<clinit>(Sys.java:116) ~[lwjgl-2.9.4-nightly-20150209.jar:?]
	at net.minecraft.client.Minecraft.getSystemTime(Minecraft.java:3159) ~[Minecraft.class:?]
	at net.minecraft.client.main.Main.main(Main.java:42) ~[Main.class:?]
	... 12 more

Full log: https://pastebin.com/jVYg2ZX8

ForgeGradle hack code:

ForgeGradle/src/main/resources/GradleStart.java

Line 84 in 6084129

sysPathsField.set(null, null);

OpenJDK 8u commit which changed the behavior: http://hg.openjdk.java.net/jdk8u/jdk8u/jdk/rev/1d666f78532a/
Corresponding OpenJDK issue: https://bugs.openjdk.java.net/browse/JDK-8235886

Possible solution:

Change hack to be like Option 2 in this post: https://stackoverflow.com/questions/15409223/adding-new-paths-for-native-libraries-at-runtime-in-java/15409446#15409446

[Barteks2x]

This is already fixed in 1.15.x, and FG2 is very unlikely to get updates anymore (because 1.12.2 is no longer supported). Especially since this only affects dev environment.

[milandamen]

@DaemonUmbra I guess that even if I made a pull request for this it would be denied?

[DaemonUmbra]

Lex has actually asked anyone who's willing to do so, to get older versions working with FG3, so I would say that would be preferable

[LexManos]

FG2 is dead due to its extreme age and hard reliance on old Gradles.
However, FG3 was specifically designed to work with ANY Minecraft version, as long as the data was there.
So if someone wishes to come along and PR to the old Forge branches to make them into FG3 workspaces, it'd be fine.

[FinnT730]

Maybe make a PR for this?

[DaemonUmbra]

Adding Forum label to kill this as any effort should go towards FG3 rather than previous versions.

[support]

👋 We use the issue tracker exclusively for final bug reports and feature requests. However, this issue appears to be better suited for the Forge Modder Support Forums. Please create a new topic on the Modder Support forum with this issue, and the conversation can continue there.