Add uncompressed trade route loading bug

Author: Trolldemorted

src/SUMMARY.md

@@ -65,6 +65,7 @@
     - [Invulnerable Ship Artillery Slots](./bugs/invulnerable-ship-artillery-slots.md)
     - [Bath House Bribes Blunders](./bugs/bath-house-bribes-blunders.md)
     - [Multiplayer Locks](./bugs/multiplayer-locks.md)
+    - [Uncompressed Trade Route Loading](./bugs/uncompressed-trade-route-loading.md)
 - [Patches](./patches.md)
     - [High Res](./patches/high-res.md)
     - [Increase Alderman "Found Settlement" Mission Limit](./patches/increase-alderman-found-settlement-limit.md)

src/bugs/uncompressed-trade-route-loading.md

@@ -0,0 +1,14 @@
+# Uncompressed Trade Route Loading
+
+## Summary
+The `decompress_packed_trade_route` function at `0x006387E0` can handle uncompressed trade routes if the output length is negative.
+However, its caller fails to allocate the correct amount of memory, so the loading fails.
+
+## Details
+Instead of calculating the absolute of the output size, the output size is `and`ed with `0x3fffffff`:
+![](uncompressed-trade-route-loading.png)
+
+For negative output sizes the result is very big, so the allocation fails, and the trade route loading is aborted.
+
+## Fix
+To fix this issue, the [correct absolute value](https://github.com/P3Modding/p3-lib/tree/master/mod-fix-uncompressed-trade-route-loading) must be calculated.