OpenJDK 12 conflict with Forge for MC 1.12.2

[Shadox]

Am a minecraft java edition user on windows 10. Using forge 14.23.5.2823 for minecraft 1.12.2. I downloaded openjdk from adoptopenjdk(java 12, openjdk version 33). In the launch options I put the javaw from openjdk as the java executable. On normal minecraft this works, but forge just says that it won't start. The log doesn't say anything except that it stopped after the narrator library for x64 was loaded. And no I don't want to use the oracle's version. Currently I want to try heavy optimization through jvm arguments and one of the big changes I want to do is use the shenandoah gc instead of the normal ones.

[quadraxis]

Only Java 8 is supported for 1.12.

[Shadox]

Ok thank you.

Edit: I know this isn't related to forge anymore, but does anybody know how to make the shenandoah GC work in minecraft 1.13? It's in the opensdk, but it just crashes the game when I put  -XX:+UseShenandoahGC in the jvm arguments. Anybody know how to make it work(it should, bcs I heard somebody used it).

Edited March 31, 2019 by Shadox