Got this error when loading up a personal mod pack in 1.12.2. (Java fully updated.)

Error: net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from Just Enough Items (jei)

FULL LOGS: https://pastebin.com/qAHAZRPA

Thanks in Advanced.

???????? it says out of memory increase your maximum ram minecraft can use....

Okay, i already have 8gb in, ill try more

Given the error message, and the fact that you only have 87 mods loaded, you may also consider trying allocating less memory, not more. Try 5 or even 4GB.

Yes, I appreciate that feels counterintuitive, but the error message isn't "I'm out of heap space", but "I've spent too much time collecting garbage".

https://pastebin.com/HSr68aJ8

New crash, changed from 3GB to 4.5GB and added the JVM Argument.

Yes, just add it to the JVM arguments. (In fact, it IS a JVM argument.)

Thanks on the personal pack question. That leaves open the possibility that it is some mod, or combination of mods, that are making life difficult for Java. I'm pretty confident that JEI is not at fault here (indeed, JEI doesn't appear in your second crash report), but that's small consolation when you just want the thing to work.

I tried 4.5GB, This is what happened.

New Crash Log: https://pastebin.com/BmBW3UpD

Phooey. Try 3GB. If that doesn't work, revert to 4.5 and add -XX:-UseGCOverheadLimit to the command line. The latter will disable the error, but may just change the problem from 'crashes' to 'locks up', which many might consider a dubious improvement.

But it might also just work, so it's worth trying.

Is this a personal pack, or is it widely available?

Okay ill try that stuff, but quick question. To add to the command line, do I add it to JVM Arguments?

Its a personal pack

That looks like the debug.log -- I don't see a crash there, although there are some exceptions being thrown by 'Nef's Medieval decoration', but I can't promise that's creating a crash. Do you have a fresh crash log?

(And I hope mezz isn't especially annoyed that we're continuing this here.)

Okay, I ran the game again. but after like 4 mins of loading it doesn't respond and crash. The exit code is -805306369.

https://pastebin.com/nFeEm3L1

Weird, I've actually never seen this error before and I had to look it up.
This isn't caused by JEI so I will close the issue, but please feel free to continue discussing and working out the error here if that's helpful!