Fraxlend (Frax Finance) contest - flyx's results

GAS Optimizations

[G-001]

++i costs less gas than i++, especially when it’s used in for-loops

FraxlendPair.sol:289 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289] for (uint256 i = 0; i < _lenders.length; i++) { change to for (uint256 i = 0; i < _lenders.length; ++i) {

Similar: FraxlendPair.sol:308 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308] FraxlendPairDeployer.sol:130 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L130] FraxlendPairDeployer.sol:158 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L158] FraxlendPairDeployer.sol:408 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L408] FraxlendWhitelist.sol:51 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L51] FraxlendWhitelist.sol:66 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L66] FraxlendWhitelist.sol:81 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81] SafeERC20.sol:24 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L24] SafeERC20.sol:28 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L28]

[G-002]

++i/i++ should be unchecked{++i}/unchecked{i++}

when it is not possible for them to overflow, as is the case when used in for- and while-loops 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: https://gist.github.com/hrkrshnn/ee8fabd532058307229d65dcd5836ddc#the-increment-in-for-loop-post-condition-can-be-made-unchecked FraxlendPair.sol:289 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289] for (uint256 i = 0; i < _lenders.length; i++) { change to for (uint256 i = 0; i < _lenders.length;) { .... unchecked {++i} }

Similar: FraxlendPair.sol:308 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308] FraxlendWhitelist.sol:51 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L51] FraxlendWhitelist.sol:66 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L66] FraxlendWhitelist.sol:81 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81] SafeERC20.sol:24 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L24] SafeERC20.sol:28 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L28] FraxlendPairCore.sol:265 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L265] FraxlendPairCore.sol:270 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L270]

[G-003]

.length should not be looked up in every loop of a for-loop

The overheads outlined below are PER LOOP, excluding the first loop

• storage arrays incur a Gwarmaccess (100 gas)
• memory arrays use MLOAD (3 gas)
• calldata arrays use CALLDATALOAD (3 gas) Caching the length changes each of these to a DUP (3 gas), and gets rid of the extra DUP needed to store the stack offset

FraxlendPair.sol:289 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289] for (uint256 i = 0; i < _lenders.length; i++) { change to uint265 lendersLength = _lenders.length for (uint256 i = 0; i < lendersLength; i++) {

Similar: FraxlendPair.sol:308 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308] FraxlendWhitelist.sol:51 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L51] FraxlendWhitelist.sol:66 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L66] FraxlendWhitelist.sol:81 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81] FraxlendPairCore.sol:265 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L265] FraxlendPairCore.sol:270 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L270]

[G-004]

Using > 0 costs more gas than != 0 when used on a uint in a require() statement

FraxlendPairCore.sol:477 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L477] FraxlendPairCore.sol:754 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L754] FraxlendPairCore.sol:835 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L477] FraxlendPairCore.sol:1000 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L1000] FraxlendPairCore.sol:1092 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L1092] FraxlendPairDeployer.sol:379 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L379] FraxlendPairDeployer.sol:380 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L380]

[G-005]

Use nested multiple if instead of && operator

If statements including conditions with the && operator can be broken down in multiple if statements to save gas.

FraxlendPair.sol:331 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L331] FraxlendPair.sol:318 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L318]

[G-006]

calldata instead of memory for read-only function parameter

If a reference type function parameter is read-only, it is cheaper in gas to use calldata instead of memory. Calldata is a non-modifiable, non-persistent area where function arguments are stored, and behaves mostly like memory. Try to use calldata as a data location because it will avoid copies and also makes sure that the data cannot be modified.

FraxlendPair.sol:46 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L46] FraxlendPair.sol:47 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L47] FraxlendPairCore.sol:152 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L152] FraxlendPairCore.sol:153 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L153] FraxlendPairCore.sol:295 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L295] FraxlendPairCore.sol:1065 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L1065] FraxlendPairDeployer.sol:193 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L193] FraxlendPairDeployer.sol:194 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L194] FraxlendPairDeployer.sol:243 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L243] FraxlendPairDeployer.sol:245 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L245] FraxlendPairDeployer.sol:246 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L246] FraxlendPairDeployer.sol:247 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L247]

[G-007]

do not initialize variables with default values

FraxlendPair.sol:289 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L289] for (uint256 i = 0; i < _lenders.length; i++) { change to for (uint256 i; i < _lenders.length; i++) {

Similar: FraxlendPair.sol:308 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPair.sol#L308] FraxlendPairDeployer.sol:127 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L127] FraxlendPairDeployer.sol:152 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L152] FraxlendPairDeployer.sol:402 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L402] FraxlendWhitelist.sol:51 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L51] FraxlendWhitelist.sol:66 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L66] FraxlendWhitelist.sol:81 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendWhitelist.sol#L81] SafeERC20.sol:22 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/libraries/SafeERC20.sol#L22] FraxlendPairCore.sol:265 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L265] FraxlendPairCore.sol:270 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairCore.sol#L270]

[G-008]

reduce require() string to 32 chars

FraxlendPairDeployer.sol:205 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L205] FraxlendPairDeployer.sol:228 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L228] FraxlendPairDeployer.sol:253 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L253] FraxlendPairDeployer.sol:365 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L365] FraxlendPairDeployer.sol:366 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L366] LinearInterestRate.sol:57 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57] LinearInterestRate.sol:61 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L61] LinearInterestRate.sol:65 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L65]

[G-009]

custom errors

Custom errors from Solidity 0.8.4 are cheaper than revert strings (cheaper deployment cost and runtime cost when the revert condition is met) while providing the same amount of information, as explained here https://blog.soliditylang.org/2021/04/21/custom-errors/ Custom errors are defined using the error statement

FraxlendPairDeployer.sol:205 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L205] FraxlendPairDeployer.sol:228 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L228] FraxlendPairDeployer.sol:253 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L253] FraxlendPairDeployer.sol:365 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L365] FraxlendPairDeployer.sol:366 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L366] FraxlendPairDeployer.sol:399 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/FraxlendPairDeployer.sol#L399] LinearInterestRate.sol:57 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57] LinearInterestRate.sol:61 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L61] LinearInterestRate.sol:65 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L65]

[G-010]

change multiple && to single require()

LinearInterestRate.sol:57 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L57] LinearInterestRate.sol:61 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L61] LinearInterestRate.sol:65 [https://github.com/code-423n4/2022-08-frax/blob/c4189a3a98b38c8c962c5ea72f1a322fbc2ae45f/src/contracts/LinearInterestRate.sol#L65]