medikko-G.md

Use defualt value rather than overwriite variable with their default value.

Overriting varibles with defualt values with their default value will waste only gas and not necessary.

There are 9 instances of this issue:

File: ./src/contracts/FraxlendPair.sol::

289:     for (uint256 i = 0; i < _lenders.length; i++) {

308:     for (uint256 i = 0; i < _borrowers.length; i++) {

File: ./src/contracts/FraxlendPairCore.sol

265:     for (uint256 i = 0; i < _approvedBorrowers.length; ++i) {

270:     for (uint256 i = 0; i < _approvedLenders.length; ++i) {

File: ./src/contracts/FraxlendPairDeployer.sol

402:     for (uint256 i = 0; i < _lengthOfArray; ) {

File: ./src/contracts/FraxlendWhitelist.sol

51:     for (uint256 i = 0; i < _addresses.length; i++) {

66:     for (uint256 i = 0; i < _addresses.length; i++) {

81:     for (uint256 i = 0; i < _addresses.length; i++) {

File: ./src/contracts/libraries/SafeERC20.sol

22: uint8 i = 0;

Use unchecked{++i}/unchecked{i++} rather than this ++i/i++ in for-loops

Using a unchecked{++i}/unchecked{i++} is recommended in for loops if underflow and overflow is not possible. This will save some gas because the compiler woudn't make a safety check. This safety checks is came from version 0.8.0 and that applies also to above versions.

There are 8 instances of this issue:

File: ./src/contracts/FraxlendPair.sol::

289:     for (uint256 i = 0; i < _lenders.length; i++) {

308:     for (uint256 i = 0; i < _borrowers.length; i++) {

File: ./src/contracts/FraxlendPairCore.sol

265:     for (uint256 i = 0; i < _approvedBorrowers.length; ++i) {

270:     for (uint256 i = 0; i < _approvedLenders.length; ++i) {

File: ./src/contracts/libraries/SafeERC20.sol

27:     for (i = 0; i < 32 && data[i] != 0; i++) {

File: ./src/contracts/FraxlendWhitelist.sol

51:     for (uint256 i = 0; i < _addresses.length; i++) {

66:     for (uint256 i = 0; i < _addresses.length; i++) {

81:     for (uint256 i = 0; i < _addresses.length; i++) {

++i/--i are more cheap operations than i++/i--

Using a ++i/--i operations can save about 6 gas for loop/instance because compiler will make less operations

There are 6 instances of this issue:

File: ./src/contracts/FraxlendPair.sol::

289:     for (uint256 i = 0; i < _lenders.length; i++) {

308:     for (uint256 i = 0; i < _borrowers.length; i++) {

File: ./src/contracts/FraxlendWhitelist.sol

51:     for (uint256 i = 0; i < _addresses.length; i++) {

66:     for (uint256 i = 0; i < _addresses.length; i++) {

81:     for (uint256 i = 0; i < _addresses.length; i++) {

File: ./src/contracts/libraries/SafeERC20.sol

27:     for (i = 0; i < 32 && data[i] != 0; i++) {

In for loop use outside variable for array length

For loop written like thisfor (uint256 i; i < array.length; ++i) { will cost more gas than for (uint256 i; i < _lengthOfArray; ++i) { because for every iteration we use mload and memory_offset that will cost about 6 gas

There are 7 instances of this issue:

File: ./src/contracts/FraxlendPair.sol

289:    for (uint256 i = 0; i < _lenders.length; i++) {

308:    for (uint256 i = 0; i < _borrowers.length; i++) {

File: ./src/contracts/FraxlendPairCore.sol:

265:    for (uint256 i = 0; i < _approvedBorrowers.length; ++i) {

270:    for (uint256 i = 0; i < _approvedLenders.length; ++i) {

File: ./src/contracts/FraxlendWhitelist.sol

51:     for (uint256 i = 0; i < _addresses.length; i++) {

66:     for (uint256 i = 0; i < _addresses.length; i++) {

81:     for (uint256 i = 0; i < _addresses.length; i++) {

Use > 0 instead of != 0 for Unsigned Integer Comparison

> 0 will save about 3 gas per loop/instance when used on unsigned integers

There are 3 instances of this issue:

File: ./src/contracts/FraxlendPairCore.sol:

257:     if (bytes(nameOfContract).length != 0) {

File: ./src/contracts/libraries/SafeERC20.sol

23:     while (i < 32 && data[i] != 0) {

27:     for (i = 0; i < 32 && data[i] != 0; i++) {

If you not use named return variables when functions returns this will wastes deployment gas because of overhead.

There are 13 instances of this issue:

File: ./src/contracts/VariableInterestRate.sol

47:     return "Variable Time-Weighted Interest Rate";

File: ./src/contracts/FraxlendPair.sol

81:     return string(abi.encodePacked("FraxlendV1 - ", collateralContract.safeSymbol(), "/",

85:     return 18;

90:     return totalAsset.shares;

97:     return address(assetContract);

101:    return totalAsset.amount;

121:    return totalAsset.toShares(_amount, false);

125:    return totalAsset.toAmount(_shares, true);

129:    return totalAsset.toShares(_amount, true);

133:    return totalAsset.toAmount(_shares, false);

145:    return totalAsset.toAmount(balanceOf(owner), false);

184:    return totalBorrow.toShares(_amount, _roundUp);

191:    return totalBorrow.toAmount(_shares, _roundUp);

File: ./src/contracts/FraxlendPairCore.sol
300:    return _totalAsset.amount - _totalBorrow.amount;
321:    return maturityDate != 0 && block.timestamp > maturityDate;

Long require()/revert() strings cost more gas.

String in require() and revert() that are bigger than 32 bytes (256 bits) will cost 3 gas for each memory work.

There are 5 instances of this issue:

File: ./src/contracts/FraxlendPairDeployer.sol

205:  require(deployedPairsBySalt[salt] == address(0), "FraxlendPairDeployer: Pair already deployed");

228:  require(_pairAddress != address(0), "FraxlendPairDeployer: create2 failed");

File: ./src/contracts/LinearInterestRate.sol

57:       require(
58:        _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest >= MIN_INT,
59:       "LinearInterestRate: _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest 60:   >= MIN_INT"
60;       );

61:       require(
62:          _maxInterest <= MAX_INT && _vertexInterest <= _maxInterest && _maxInterest > MIN_INT,"LinearInterestRate: 
63:        _maxInterest <= MAX_INT && _vertexInterest <= _maxInterest && _maxInterest > MIN_INT"
64:        );

65        require(
66            _vertexUtilization < MAX_VERTEX_UTIL && _vertexUtilization > 0,
67            "LinearInterestRate: _vertexUtilization < MAX_VERTEX_UTIL && _vertexUtilization > 0"
68        );

Use custom errors rather than revert()/require() strings to save gas

Custom errors are available from solidity 0.8.4 and above. The code below match that and using them will save gas each time they're hit by avoiding having to allocate and store the revert string.

There are 5 instances of this issue:

File: ./src/contracts/FraxlendPairDeployer.sol

205:  require(deployedPairsBySalt[salt] == address(0), "FraxlendPairDeployer: Pair already deployed");

228:  require(_pairAddress != address(0), "FraxlendPairDeployer: create2 failed");

File: ./src/contracts/LinearInterestRate.sol

57:       require(
58:        _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest >= MIN_INT,
59:       "LinearInterestRate: _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest 60:   >= MIN_INT"
60;       );

61:       require(
62:          _maxInterest <= MAX_INT && _vertexInterest <= _maxInterest && _maxInterest > MIN_INT,"LinearInterestRate: 
63:        _maxInterest <= MAX_INT && _vertexInterest <= _maxInterest && _maxInterest > MIN_INT"
64:        );

65        require(
66            _vertexUtilization < MAX_VERTEX_UTIL && _vertexUtilization > 0,
67            "LinearInterestRate: _vertexUtilization < MAX_VERTEX_UTIL && _vertexUtilization > 0"
68        );

Replace x <= y with x < y + 1, and x >= y with x > y - 1

In the EVM machine command for <=/>= doesn't exist rather than two operations are performed >/< and = that will cost more gas than using one comparison operator.

There are 14 instances of this issue:

File: ./src/contracts/FraxlendPairCore.sol

315:         return _ltv <= maxLTV;

472:         _interestEarned + _totalBorrow.amount <= type(uint128).max &&

473:         _interestEarned + _totalAsset.amount <= type(uint128).max

525:         if (_answer <= 0) {

533:         if (_answer <= 0) {

988:         _collateralForLiquidator = _leftoverCollateral <= 0

1000:        if (_leftoverCollateral <= 0) {

File:  ./src/contracts/FraxlendPairDeployer.sol

365:         require(_maxLTV <= GLOBAL_MAX_LTV, "FraxlendPairDeployer: _maxLTV is too large");

File:  ./src/contracts/FraxlendPairHelper.sol

134:         if (_answer <= 0) {

142:         if (_answer <= 0) {

284:         _collateralForLiquidator = _leftoverCollateral <= 0

292:         if (_leftoverCollateral <= 0 && (_borrowerShares - _sharesToLiquidate) > 0) {

File:  ./src/contracts/LinearInterestRate.sol

58:          _minInterest < MAX_INT && _minInterest <= _vertexInterest && _minInterest >= MIN_INT,

62:          _maxInterest <= MAX_INT && _vertexInterest <= _maxInterest && _maxInterest > MIN_INT,

<x> += <y> is more expensive than <x> = <x> + <y> for state variables

There are 11 instances of this issue:

File: ./src/contracts/FraxlendPairCore.sol

475:         _totalBorrow.amount += uint128(_interestEarned);

476:         _totalAsset.amount += uint128(_interestEarned);

484:         _totalAsset.shares += uint128(_feesShare);

566:         _totalAsset.amount += _amount;

567:         _totalAsset.shares += _shares;

718:         _totalBorrow.amount += _borrowAmount;

719:         _totalBorrow.shares += uint128(_sharesAdded);

724:         userBorrowShares[msg.sender] += _sharesAdded;

772:         userCollateralBalance[_borrower] += _collateralAmount;

773:         totalCollateral += _collateralAmount;

File ./src/test/e2e/BasePairTest.sol

539:          _sumOfInt += _interestEarned;