Paper/patches/server/0439-Fix-missing-chunks-due-to-integer-overflow.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: David Slovikosky <davidslovikosky@gmail.com>
Date: Tue, 9 Jun 2020 00:10:03 -0700
Subject: [PATCH] Fix missing chunks due to integer overflow

This patch fixes a bug in the WorldChunkManagerTheEnd class where the distance
from 0,0 squared overflows the maximum size of an integer. The overflow leads
to hard chunk borders around 370,000 blocks from 0,0. After this cutoff there
is a few hundred thousand block gap before end land resuming to generate at
530,000 blocks from spawn. This is due to the integer flipping back and forth.

The fix for the issue is quite simple, casting chunk coordinates to longs
allows the distance calculation to avoid overflow and work as intended.

diff --git a/src/main/java/net/minecraft/world/level/biome/TheEndBiomeSource.java b/src/main/java/net/minecraft/world/level/biome/TheEndBiomeSource.java
index 9a704c45f1afa82ff8d9ee3fa1e2437c1d4ec875..d090bdc063480ee6e28b0d60447ebe4063e6d688 100644
--- a/src/main/java/net/minecraft/world/level/biome/TheEndBiomeSource.java
+++ b/src/main/java/net/minecraft/world/level/biome/TheEndBiomeSource.java
@@ -85,7 +85,7 @@ public class TheEndBiomeSource extends BiomeSource {
         int l = j / 2;
         int m = i % 2;
         int n = j % 2;
-        float f = 100.0F - Mth.sqrt((float)(i * i + j * j)) * 8.0F;
+        float f = 100.0F - Mth.sqrt((long) i * (long) i + (long) j * (long) j) * 8.0F; // Paper - cast ints to long to avoid integer overflow
         f = Mth.clamp(f, -100.0F, 80.0F);
 
         for(int o = -12; o <= 12; ++o) {