Canto v2 contest - Fitraldys's results

1. Use Custom Error instead of Revert / Require 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 / require error strings with custom error.

POC :

https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L256 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L275 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L289 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L306 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L312 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L416 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L434 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L524 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L526 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L527 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L104 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L106 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L122 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L123 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L151 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L241 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L246 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L313 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L314 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L405 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L420 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L433 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L435 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L446 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L448 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L470 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/WETH.sol#L29 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/WETH.sol#L69 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/WETH.sol#L72 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L25 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L26 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L27 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L45 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L46 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L47 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L76 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L85 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L128 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L129 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L140 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L158 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L183 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L242 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L335 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L348 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L356 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L378 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L496 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L561 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Comptroller.sol#L619 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Accountant/AccountantDelegator.sol#L42 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Accountant/AccountantDelegator.sol#L43 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Accountant/AccountantDelegator.sol#L123 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Accountant/AccountantDelegate.sol#L87 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Accountant/AccountantDelegate.sol#L101 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Treasury/TreasuryDelegator.sol#L31 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Treasury/TreasuryDelegator.sol#L32 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/CNote.sol#L17 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/CNote.sol#L94 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/CNote.sol#L105

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/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L289 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L306

3. useage of uint / int smaller than 32 bytes incurs overhead

When using elements that are smaller than 32 bytes, your contract’s gas usage may be higher. This is because the EVM operates on 32 bytes at a time. Therefore, if the element is smaller than that, the EVM must use more operations in order to reduce the size of the element from 32 bytes to the desired size.

resource : https://docs.soliditylang.org/en/v0.8.11/internals/layout_in_storage.html

Use a larger size then downcast where needed

POC :

https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L43 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-core.sol#L524 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L350 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L369 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Stableswap/BaseV1-periphery.sol#L491 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/WETH.sol#L8

4. Consider making some constants as non-public to save gas

Reducing from public to private or internal can save gas when a constant isn’t used outside of its contract. I suggest changing the visibility from public to internal or private.

POC :

https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/Governance/GovernorBravoDelegate.sol#L12 https://github.com/Plex-Engineer/lending-market-v2/blob/main/contracts/NoteInterest.sol#L20