prePO contest - Kiep's results

1. No need to initialize variables with default values

Source file : https://github.com/code-423n4/2022-03-prepo/blob/main/contracts/core/AccountAccessController.sol

Finding : In this loops at line 44-47 value is set 0. If a variable is not set/initialized, it is assumed to have the default value (0, false, 0x0 etc depending on the data type). So we can save gas.

for (uint256 _i = 0; _i < _accounts.length; _i++) {
            _allowedAccounts[_allowedAccountsIndex][_accounts[_i]] = true;
            emit AccountAllowed(_accounts[_i]);
        }

Change to

for (uint256 _i; _i < _accounts.length; _i++) {
            _allowedAccounts[_allowedAccountsIndex][_accounts[_i]] = true;
            emit AccountAllowed(_accounts[_i]);
        }

Other line at 55-58.

2. Better using ++i than i++ to save gas Source file : https://github.com/code-423n4/2022-03-prepo/blob/main/contracts/core/AccountAccessController.sol

Finding : Using i++ in loop is more expensive than ++i. For example, using remix to declare variable i and using i++ we need 43446 and when we use ++i we need 43440. If we use this in loops, we will need more gas each loop. Change to this:

for (uint256 _i; _i < _accounts.length; ++_i) {
            _allowedAccounts[_allowedAccountsIndex][_accounts[_i]] = true;
            emit AccountAllowed(_accounts[_i]);
        }

Other line at 55-58

3. Using ternary operator to save more gas and readability Source file : https://github.com/code-423n4/2022-03-prepo/blob/main/contracts/core/CollateralDepositRecord.sol

Finding : If we want to save more line of code, readability and gas, we can use a ternary operator. In line 46-55 we have this 2 if-else conditional statement.

if (_globalDepositAmount > _amount) {
            _globalDepositAmount -= _amount;
        } else {
            _globalDepositAmount = 0;
        }
        if (_accountToNetDeposit[_sender] > _amount) {
            _accountToNetDeposit[_sender] -= _amount;
        } else {
            _accountToNetDeposit[_sender] = 0;
        }

///gas cost is 89098

Change to :

_globalDepositAmount = _globalDepositAmount > _amount ? _globalDepositAmount -= _amount : 0;
        _accountToNetDeposit[_sender] = _accountToNetDeposit[_sender] > _amount ? _accountToNetDeposit[_sender] -= _amount : 0;

/// gas cost is 70632