From fe2227ef535b411faffacc19a2fab16be8fa4e09 Mon Sep 17 00:00:00 2001
From: Gonza Montiel <gonzamontiel@users.noreply.github.com>
Date: Wed, 21 Jan 2026 16:25:57 -0300
Subject: [PATCH] =?UTF-8?q?fix:=20=F0=9F=94=A7=20account=20for=20storage?=
 =?UTF-8?q?=20reads=20on=20withdrawal=20(#407)?=
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## Summary
ERC20 balances precompile `withdraw()` was failing to account for gas
costs associated with storage reads. In fact the function was calling
`usable_balance` without accounting for `record_db_read`.

## Changes
- Added `116 bytes` of storage read computed like this: `Blake2128(16) +
AccountId(20) + AccountInfo ((4 * 4) + AccountData(16 * 4))`, to cover
for `usable_balance`, following the same that `balance_of` does.
---
 operator/precompiles/erc20-balances/src/lib.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/operator/precompiles/erc20-balances/src/lib.rs b/operator/precompiles/erc20-balances/src/lib.rs
index 3800244e..af0a0032 100644
--- a/operator/precompiles/erc20-balances/src/lib.rs
+++ b/operator/precompiles/erc20-balances/src/lib.rs
@@ -446,6 +446,9 @@ where
         let account_amount: U256 = {
             let owner: Runtime::AccountId =
                 Runtime::AddressMapping::into_account_id(handle.context().caller);
+            // frame_system::Account:
+            // Blake2128(16) + AccountId(20) + AccountInfo ((4 * 4) + AccountData(16 * 4))
+            handle.record_db_read::<Runtime>(116)?;
             pallet_balances::Pallet::<Runtime, Instance>::usable_balance(&owner).into()
         };