I've been trying to use Forge for a 1.12.2 mod using the Prism Launcher and I've been getting crashes with exit code 6.

The console log is this.

I've tried running Optifine as a test mod and I have tried running with no mods, but both gave the same result.

Same issue with another Launcher like MultiMC or AT Launcher?

I haven't tried any other launchers, but I was getting the same results when I tried using forge with the vanilla launcher.

Maybe it refers to an issue with the system - check for CPU/GPU driver updates

I checked for any driver updates, but no new updates were found

Keep on using the original Launcher

Run Vanilla 1.12.2 once and close the game

Download Optifine and run optifine as installer (click on the optifine jar)

Start the launcher and make sure the Optifine profile is selected - then test it again

 

I tried both Vanilla and Optfine like you said, and both gave the same result. So I believe the issue is most likely with Minecraft in general and not Forge

Does it work with newer versions?

For 1.16.5 also make a test with Embeddium + Oculus as Optifine replacement

Edited June 13Jun 13 by TileEntity

Of the newer versions I have tested, 1.21.5 does work perfectly fine, but the only others I have tried, being 1.12.2 and now 1.16.5 with the mods you suggested showing the same results of crashing with exit code 6.

Maybe it refers to an issue with Java 8

 

Install this version:

https://www.azul.com/downloads/?version=java-8-lts&os=windows&architecture=x86-64-bit&package=jre#zulu

In your Launcher, change the Java Executable o the new java 8 installation at

C:\Program Files\Zulu\zulu-8-jre\bin\javaw.exe

I've tried the java version you linked to and got a new exit code of 127

Here is the new console log

I also tried making sure that I had Java 8 selected with the version of Java 8 I already had installed and got the same exit code

Here is the console log with that installation in case it has any differences

I do notice both say 'Java checker returned some invalid data we don't understand:' followed by 'Minecraft might not start properly.' which could be some issues.

 

Are you using linux? The paths don't look like Windows paths.

Can you run java --version from the commandline if so?

I am using Linux, I did Java --version and it shows I have Java 8 installed

But your Launcher does not find it
 

Java path is:
/run/user/1000/doc/3f910b8/java

Checking Java version...
Java checker returned some invalid data we don't understand:

Check the Azul Zulu site and select your OS and download the latest Java 8 build for Linux

https://www.azul.com/downloads/?version=java-8-lts&package=jre#zulu

After installation, check the path and put this path into your Launcher Java settings (Java Executable)

I redownloaded Java 8 and manually put the path and it worked, thank you.