From a59d8a4482828c890c3f6e60abd0c7c070232d6e Mon Sep 17 00:00:00 2001
From: Dirk Brink <hello@dirk.tech>
Date: Fri, 22 Dec 2023 10:22:38 -0800
Subject: [PATCH] evm: wipe slots with warnings

---
 .../CircleIntegration/Implementation.sol         | 16 ++++++++++++++++
 evm/src/contracts/CircleIntegration/Storage.sol  |  9 +++++++++
 2 files changed, 25 insertions(+)

diff --git a/evm/src/contracts/CircleIntegration/Implementation.sol b/evm/src/contracts/CircleIntegration/Implementation.sol
index e587c7b..b0923eb 100644
--- a/evm/src/contracts/CircleIntegration/Implementation.sol
+++ b/evm/src/contracts/CircleIntegration/Implementation.sol
@@ -15,6 +15,22 @@ contract Implementation is Logic {
     function initialize() public virtual initializer {
         // This function needs to be exposed for an upgrade to pass. Any additional logic can be
         // placed here.
+
+        /**
+         * WARNING: This snippet should be removed for any following contract upgrades
+         * We are using the below snippet to reset storage slots that are no longer being used
+         * for safety and to free them up for future use. We don't want to inadvertantly wipe
+         * the same slots on future upgrades. See Storage.sol for reasoning.
+         */
+        assembly ("memory-safe") {
+            sstore(0x0, 0x0)
+            sstore(0x1, 0x0)
+            sstore(0x2, 0x0)
+            sstore(0x3, 0x0)
+            sstore(0x4, 0x0)
+            sstore(0xA, 0x0)
+        }
+
     }
 
     modifier initializer() {
diff --git a/evm/src/contracts/CircleIntegration/Storage.sol b/evm/src/contracts/CircleIntegration/Storage.sol
index fc24e98..16eba9c 100644
--- a/evm/src/contracts/CircleIntegration/Storage.sol
+++ b/evm/src/contracts/CircleIntegration/Storage.sol
@@ -2,6 +2,15 @@
 
 pragma solidity ^0.8.22;
 
+
+/**
+ * WARNING: This is the state layout of V0 before the first upgrade.
+ * Slots 0 -> 4 inclusive and slot 10 will be wiped to 0 on initialisation of the new
+ * implementation and will be safe to use again in the future. We are no longer
+ * using those variables in state, but they are instead immutables in the new implementation.
+ * If using those slots again, ensure the slots are not being wiped to 0 in the
+ * initialiser in future upgrades. 
+ */
 /**
  * struct State {
  *         // state.slot := 0x0