# Unnecessary Recomputation of Storage Pointer in MToken._startEarning Low/Info · Three Sigma · Stablecoin framework · 8th January, 2024 Finding 3S-M^0-N04 of the M^0 Minter Gateway security review. - Protocol: https://www.m0.org/ - Report: /reports/m-0 - Codebase: https://github.com/0xsimao/ttg/tree/a8127901fa1f24a2e821cf4d9854a1aa6ac8088c - Source: https://cdn.sanity.io/files/qoqld077/production/1cdafafad874aba76e062ad8c216c98338c096db.pdf --- ### Description In [MToken._startEarning](https://github.com/MZero-Labs/protocol/blob/3499f50ff3382729f3e59565b19386ba61ef8e36/src/MToken.sol#L239) function, the _balances mapping is stored in the mBalance_ variable. MBalance storage mBalance_ = _balances[account_]; But a few lines below, instead of using mBalance_ to retrieve rawBalance, _balances[account].rawBalance is used again spending unnecessary gas. ```solidity function _startEarning(address account_) internal { emit StartedEarning(account_); MBalance storage mBalance_ = _balances[account_]; if (mBalance_.isEarning) return; mBalance_.isEarning = true; // Treat the raw balance as present amount for non earner. uint240 amount_ = _balances[account_].rawBalance; ``` ### Recommendation Change the amount_ variable to: uint240 amount_ = mBalance_.rawBalance; ### Status Addressed in [#fc9069a](https://github.com/MZero-Labs/protocol/commit/fc9069a2c3b4e2f3de43d4c1e51d3406cc7b21e5).