Foundry DeFi Stablecoin CodeHawks Audit Contest
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Severity: gas
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Gas Optimizations

Mlome

Gas Optimizations

Issue Instances
[GAS-01] Add non-zero check before calling function inside loop 1
[GAS-02] Use == 0 instead of <= 0 for uint 2
[GAS-03] Increments can be unchecked 2
[GAS-04] Setting the constructor to payable 2

[GAS-01] Add non-zero check before calling function inside loop

The function getAccountCollateralValue() calls getUsdValue() which is very gas consuming for each token of the s_collateralTokens array even if the amount is 0 which case always returns 0.

Instance (1):

File: DSCEngine.sol
350: function getAccountCollateralValue(address user) public view returns (uint256 totalCollateralValueInUsd) {
// loop through each collateral token, get the amount they have deposited, and map it to
// the price, to get the USD value
for (uint256 i = 0; i < s_collateralTokens.length; i++) {
address token = s_collateralTokens[i];
uint256 amount = s_collateralDeposited[user][token];
totalCollateralValueInUsd += getUsdValue(token, amount); // @audit - [GAS] Add non 0 check
}
return totalCollateralValueInUsd;
}
​

Apply this edit to avoid calling getUsdValue() on 0 amount

File: DSCEngine.sol
350: function getAccountCollateralValue(address user) public view returns (uint256 totalCollateralValueInUsd) {
// loop through each collateral token, get the amount they have deposited, and map it to
// the price, to get the USD value
for (uint256 i = 0; i < s_collateralTokens.length; i++) {
address token = s_collateralTokens[i];
uint256 amount = s_collateralDeposited[user][token];
+ if (amount != 0) {
totalCollateralValueInUsd += getUsdValue(token, amount);
+ }
}
return totalCollateralValueInUsd;
}
​

[GAS-02] Use == 0 instead of <= 0 for uint

uint cannot be less than 0, so == 0 is a sufficient check

Instances (2):

File: DecentralizedStableCoin.sol
48: if (_amount <= 0) { // @audit - uint256 can not be < 0
​
61: if (_amount <= 0) { // @audit - uint256 can not be < 0
​

[GAS-03] Increments can be unchecked

Increments in for loops as well as some uint256 iterators cannot realistically overflow as this would require too many iterations, so this can be unchecked.
The unchecked keyword is new in solidity version 0.8.0, so this only applies to that version or higher, which these instances are. This saves 30-40 gas PER LOOP.

Instances (2):

File: DSCEngine.sol
118: for (uint256 i = 0; i < tokenAddresses.length; i++) {
​
353: for (uint256 i = 0; i < s_collateralTokens.length; i++) {
​

[GAS-04] Setting the constructor to payable

Saves ~13 gas per instance

Instances (2):

File: DecentralizedStableCoin.sol
44: constructor() ERC20("DecentralizedStableCoin", "DSC") {}
​
File: DSCEngine.sol
112: constructor(address[] memory tokenAddresses, address[] memory priceFeedAddresses, address dscAddress) {
​

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