Canto contest - Fitraldys's results

1. Use Custom Error instead of Revert String to Save Gas

Custom error from solidity 0.8.4 are cheaper than revert strings, custom error are defined using the error statement can use inside and outside the contract.

source https://blog.soliditylang.org/2021/04/21/custom-errors/

i suggest replacing revert error strings with custom error

POC :

https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L253 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L286 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L288 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L294 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L303 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L309 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L413 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L431 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L521 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L523 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-core.sol#L524 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L71 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L86 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L88 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L104 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L105 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L133 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L223 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L228 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L295 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L296 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L387 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L402 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L415 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L417 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L428 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L430 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L452 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L466 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/WETH.sol#L29 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/WETH.sol#L96 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/WETH.sol#L97 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L25 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L26 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L27 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L45 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L46 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L47 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L78 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L87 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L115 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L132 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L133 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L146 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L164 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L182 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L187 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L178 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L237 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L343 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L351 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L373 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L491 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L556 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L614 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegator.sol#L43 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegator.sol#L44 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegator.sol#L124 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegate.sol#L17 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegate.sol#L18 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegate.sol#L29 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegate.sol#L48 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegate.sol#L60 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Accountant/AccountantDelegate.sol#L83 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Treasury/TreasuryDelegator.sol#L31 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Treasury/TreasuryDelegator.sol#L32

2. > 0 is less efficient than != 0 for unsigned integers

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

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.

source : https://twitter.com/gzeon/status/1485428085885640706

I suggest changing > 0 with != 0

POC :

https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L104 https://github.com/Plex-Engineer/stableswap/blob/489d010eb99a0885139b2d5ed5a2d826838cc5f9/contracts/BaseV1-periphery.sol#L105

3. consider to change constant to immutable to save gas

constant variables are implemented (replacements at compile-time), an expression assigned to a constant variable is recomputed each time that the variable is used, which wastes some gas.

If the variable was immutable instead: the calculation would only be done once at deploy time (in the constructor), and then the result would be saved and read directly at runtime rather than being recalculated.

source https://github.com/ethereum/solidity/issues/9232

POC :

https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Governance/GovernorBravoDelegate.sol#L12 https://github.com/Plex-Engineer/lending-market/blob/755424c1f9ab3f9f0408443e6606f94e4f08a990/contracts/Comptroller.sol#L79