xTRIBE contest - Scocco's results

Bad Comparison with Zero

Impact

In If conditionals, prefer to use !=0 than > 0 when possible to save Gas

Proof of Concept

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/FlywheelCore.sol#L167

167┆ if (oldRewardBalance > 0) {
168┆     rewardToken.safeTransferFrom(address(flywheelRewards), address(newFlywheelRewards), oldRewardBalance);
169┆ }

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/FlywheelCore.sol#L218

218┆ if (strategyRewardsAccrued > 0) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20Gauges.sol#L467

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20Gauges.sol#L487

467┆ if (weight > 0) {
⋮┆----------------------------------------
487┆ if (weight > 0) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20MultiVotes.sol#L287

287┆ if (pos > 0 && ckpts[pos - 1].fromBlock == block.number) {

Tools Used

Static code analysis

Recommended Mitigation steps

Replace the > 0 to != 0

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/FlywheelCore.sol#L167

167┆ if (oldRewardBalance != 0) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/FlywheelCore.sol#L218

218┆ if (strategyRewardsAccrued != 0) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20Gauges.sol#L467

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20Gauges.sol#L487

467┆ if (weight != 0) {
⋮┆----------------------------------------
487┆ if (weight != 0) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20MultiVotes.sol#L287

287┆ if (pos != 0 && ckpts[pos - 1].fromBlock == block.number) {

Postfix to Prefix

Impact

There is no risk of overflow caused by increasing the iteration index in for loops (the ++i in for (uint256 i = 0; i < numIterations; ++i)), but increments perform overflow checks that are not needed in this case.

So, to save gas, prefer ++i to i++ in loops.

Proof of Concept

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/rewards/FlywheelGaugeRewards.sol#L189

189┆ for (uint256 i = 0; i < size; i++) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20MultiVotes.sol#L346

346┆ for (uint256 i = 0; i < size && (userFreeVotes + totalFreed) < votes; i++) {

Tools Used

Static code analysis

Recommended Mitigation steps

To save gas, prefer ++i to i++ in loops.

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/rewards/FlywheelGaugeRewards.sol#L189

189┆ for (uint256 i = 0; i < size; ++i) {

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20MultiVotes.sol#L346

346┆ for (uint256 i = 0; i < size && (userFreeVotes + totalFreed) < votes; ++i) {