Gas: > 0 is less efficient than != 0 for unsigned integers (with proof)

[code423n4]

Handle

Dravee

Vulnerability details

Impact

!= 0 costs less gas compared to > 0 for unsigned integers in require statements with the optimizer enabled (6 gas)

Proof: While it may seem that > 0 is cheaper than !=, this is only true without the optimizer enabled and outside a require statement. If you enable the optimizer at 10k AND you're in a require statement, this will save gas. You can see this tweet for more proofs: https://twitter.com/gzeon/status/1485428085885640706

Proof of Concept

> 0 in require statements are used in the following location(s):

contracts\dex\bsc\UniV2ClassDex.sol:199:        require(amountIn > 0, 'INSUFFICIENT_INPUT_AMOUNT');
contracts\dex\bsc\UniV2ClassDex.sol:200:        require(reserveIn > 0 && reserveOut > 0, 'INSUFFICIENT_LIQUIDITY');
contracts\dex\bsc\UniV2ClassDex.sol:208:        require(amountOut > 0, 'INSUFFICIENT_OUTPUT_AMOUNT');
contracts\dex\bsc\UniV2ClassDex.sol:209:        require(reserveIn > 0 && reserveOut > 0, 'INSUFFICIENT_LIQUIDITY');
contracts\dex\eth\UniV2Dex.sol:197:        require(amountIn > 0, 'INSUFFICIENT_INPUT_AMOUNT');
contracts\dex\eth\UniV2Dex.sol:198:        require(reserveIn > 0 && reserveOut > 0, 'INSUFFICIENT_LIQUIDITY');
contracts\dex\eth\UniV2Dex.sol:206:        require(amountOut > 0, 'INSUFFICIENT_OUTPUT_AMOUNT');
contracts\dex\eth\UniV2Dex.sol:207:        require(reserveIn > 0 && reserveOut > 0, 'INSUFFICIENT_LIQUIDITY');
contracts\dex\eth\UniV3Dex.sol:126:        require(secondsAgo > 0, "SecondsAgo must >0");
contracts\dex\eth\UniV3Dex.sol:165:        require(amount0Delta > 0 || amount1Delta > 0);
contracts\farming\FarmingPools.sol:96:        require(amount > 0, "Cannot stake 0");
contracts\farming\FarmingPools.sol:104:        require(amount > 0, "Cannot withdraw 0");
contracts\gov\GovernorAlpha.sol:248:        require(proposalCount >= proposalId && proposalId > 0, "GovernorAlpha::state: invalid proposal id");
contracts\liquidity\LPool.sol:57:        require(initialExchangeRateMantissa > 0, "Initial Exchange Rate Mantissa should be greater zero");
contracts\liquidity\LPool.sol:674:            require(balanceAfter > balanceBefore, 'mint 0');
contracts\ControllerV1.sol:311:        require(rewards > 0, 'rewards is zero');
contracts\ControllerV1.sol:342:        require(supplyAmount > 0 || borrowAmount > 0, 'amount is less than 0');
contracts\ControllerV1.sol:358:        require(supplyAmount > 0 || borrowAmount > 0, 'amount0 and amount1 is 0');
contracts\OLETokenLock.sol:46:        require(amount > 0, "no amount available");
contracts\OLETokenLock.sol:57:        require(releaseVars[beneficiary].amount > 0, 'beneficiary does not exist');
contracts\OLETokenLock.sol:75:        require(releaseVar.amount > 0, "beneficiary does not exist");
contracts\OpenLevV1Lib.sol:81:        require(defaultFeesRate < 10000 && insuranceRatio < 100 && defaultMarginLimit > 0 && updatePriceDiscount <= 100
contracts\OpenLevV1Lib.sol:82:        && feesDiscount <= 100 && penaltyRatio < 10000 && twapDuration > 0, 'PRI');
contracts\OpenLevV1Lib.sol:112:        require(feesRate < 10000 && marginLimit > 0 && dexs.length > 0, 'PRI');
contracts\OpenLevV1Lib.sol:297:            require(borrow > 0, "BB0");
contracts\Reserve.sol:32:        require(amount > 0, "amount is 0!");
contracts\XOLE.sol:71:        require(totalSupply > 0, "Can't share without locked OLE");
contracts\XOLE.sol:252:        require(_value > 0, "Non zero value");
contracts\XOLE.sol:266:        require(_value > 0, "need non - zero value");
contracts\XOLE.sol:267:        require(_locked.amount > 0, "No existing lock found");
contracts\XOLE.sol:279:        require(_locked.amount > 0, "Nothing is locked");

Tools Used

VS Code

Recommended Mitigation Steps

Change > 0 with != 0 in require statements. Also, enable the Optimizer.

[ColaM12]

Duplicate to #21