Frax Ether Liquid Staking contest - zishansami's results

Gas Optimizations

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G-01: pre-increment ++i/--i costs less gas than post-increment i++/i--

Saves 6 gas per loop in a for loop

Total instances of this issue: 1

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L84

src/ERC20/ERC20PermitPermissionedMint.sol

84:        for (uint i = 0; i < minters_array.length; i++){ 

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G-02: ++i/i++ should be placed in unchecked blocks to save gas as it is impossible for them to overflow in for and while loops

Unchecked keyword is available in solidity version 0.8.0 or higher and can be applied to iterator variables to save gas. Saves more than 30 gas per loop.

Total instances of this issue: 5

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L84

src/ERC20/ERC20PermitPermissionedMint.sol

84:        for (uint i = 0; i < minters_array.length; i++){ 

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L129

src/frxETHMinter.sol

129:        for (uint256 i = 0; i < numDeposits; ++i) {

instance #3 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L63

src/OperatorRegistry.sol

63:        for (uint256 i = 0; i < arrayLength; ++i) {

instance #4 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L84

src/OperatorRegistry.sol

84:        for (uint256 i = 0; i < times; ++i) {

instance #5 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L114

src/OperatorRegistry.sol

114:            for (uint256 i = 0; i < original_validators.length; ++i) {

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G-03: Length of the array (<array>.length) need not be looked up in every iteration of a for-loop

Reading array length at each iteration of the loop takes total 6 gas (3 for mload and 3 to place memory_offset) in the stack. Caching the array.length saves around 3 gas per iteration.

Total instances of this issue: 2

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L84

src/ERC20/ERC20PermitPermissionedMint.sol

84:        for (uint i = 0; i < minters_array.length; i++){ 

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L114

src/OperatorRegistry.sol

114:            for (uint256 i = 0; i < original_validators.length; ++i) {

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G-04: x += y costs more gas than x = x + y for state variables

Total instances of this issue: 2

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L97

src/frxETHMinter.sol

97:            currentWithheldETH += withheld_amt;

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L72

lib/ERC4626/src/xERC4626.sol

72:        storedTotalAssets += amount;

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G-05: Put subtractions operation in unchecked {} block where the variable cannot underflow because of a previous require()

require(a <= b); x = b - a ==> require(a <= b); unchecked { x = b - a }

Total instances of this issue: 1

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L168

src/frxETHMinter.sol

168:        currentWithheldETH -= amount;

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G-06: No need to compare boolean expressions with boolean literals, directly use the expression

if (<x> == true) ==> if (<x>) if (<x> == false) => if (!<x>)

Total instances of this issue: 3

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L46

src/ERC20/ERC20PermitPermissionedMint.sol

46:       require(minters[msg.sender] == true, "Only minters");

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L68

src/ERC20/ERC20PermitPermissionedMint.sol

68:        require(minters[minter_address] == false, "Address already exists");

instance #3 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L78

src/ERC20/ERC20PermitPermissionedMint.sol

78:        require(minters[minter_address] == true, "Address nonexistant");

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G-07: No need to initialize non-constant/non-immutable variables to zero

Since the default value is already zero, overwriting is not required. Saves 8 gas per instance.

Total instances of this issue: 6

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/ERC20/ERC20PermitPermissionedMint.sol#L84

src/ERC20/ERC20PermitPermissionedMint.sol

84:        for (uint i = 0; i < minters_array.length; i++){ 

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L94

src/frxETHMinter.sol

94:        uint256 withheld_amt = 0;

instance #3 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L129

src/frxETHMinter.sol

129:        for (uint256 i = 0; i < numDeposits; ++i) {

instance #4 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L63

src/OperatorRegistry.sol

63:        for (uint256 i = 0; i < arrayLength; ++i) {

instance #5 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L84

src/OperatorRegistry.sol

84:        for (uint256 i = 0; i < times; ++i) {

instance #6 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/OperatorRegistry.sol#L114

src/OperatorRegistry.sol

114:            for (uint256 i = 0; i < original_validators.length; ++i) {

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G-08: Using uints/ints smaller than 256 bits increases overhead

Gas usage becomes higher with uint/int smaller than 256 bits because EVM operates on 32 bytes and uses additional operations to reduce the size from 32 bytes to the target size.

Total instances of this issue: 12

instance #1 Permalink: https://github.com/code-423n4/2022-09-frax/blob/main/src/sfrxETH.sol#L42-L45

src/sfrxETH.sol

42:    constructor(ERC20 _underlying, uint32 _rewardsCycleLength)
43:        ERC4626(_underlying, "Staked Frax Ether", "sfrxETH")
44:        xERC4626(_rewardsCycleLength)
45:    {}

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L24

lib/ERC4626/src/xERC4626.sol

24:    uint32 public immutable rewardsCycleLength;

instance #3 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L27

lib/ERC4626/src/xERC4626.sol

27:    uint32 public lastSync;

instance #4 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L30

lib/ERC4626/src/xERC4626.sol

30:    uint32 public rewardsCycleEnd;

instance #5 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L33

lib/ERC4626/src/xERC4626.sol

33:    uint192 public lastRewardAmount;

instance #6 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L37

lib/ERC4626/src/xERC4626.sol

37:    constructor(uint32 _rewardsCycleLength) {

instance #7 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L48

lib/ERC4626/src/xERC4626.sol

48:        uint192 lastRewardAmount_ = lastRewardAmount;

instance #8 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L49

lib/ERC4626/src/xERC4626.sol

49:        uint32 rewardsCycleEnd_ = rewardsCycleEnd;

instance #9 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L50

lib/ERC4626/src/xERC4626.sol

50:        uint32 lastSync_ = lastSync;

instance #10 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L79

lib/ERC4626/src/xERC4626.sol

79:        uint192 lastRewardAmount_ = lastRewardAmount;

instance #11 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L80

lib/ERC4626/src/xERC4626.sol

80:        uint32 timestamp = block.timestamp.safeCastTo32();

instance #12 Link: https://github.com/code-423n4/2022-09-frax/blob/main/lib/ERC4626/src/xERC4626.sol#L89

lib/ERC4626/src/xERC4626.sol

89:        uint32 end = ((timestamp + rewardsCycleLength) / rewardsCycleLength) * rewardsCycleLength;

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G-09: Using != 0 costs less gas than > 0 in a require() statement

Saves 6 gas per instance for solidity version less than 0.8.12.

Total instances of this issue: 2

instance #1 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L79

src/frxETHMinter.sol

79:        require(sfrxeth_recieved > 0, 'No sfrxETH was returned');

instance #2 Link: https://github.com/code-423n4/2022-09-frax/blob/main/src/frxETHMinter.sol#L126

src/frxETHMinter.sol

126:        require(numDeposits > 0, "Not enough ETH in contract");