Y2k Finance contest - prasantgupta52's results

1. ++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

Instances:

// Links to github files Vault.sol:L443

Actual Codes Used:

src/Vault.sol:443:        for (uint256 i = 0; i < epochsLength(); i++) {

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2.++I COSTS LESS GAS COMPARED TO I++ OR I += 1

Pre-increments and pre-decrements are cheaper.

For a uint256 i variable, the following is true with the Optimizer enabled at 10k: Increment: i += 1 is the most expensive form i++ costs 6 gas less than i += 1 ++i costs 5 gas less than i++ (11 gas less than i += 1)

Note that post-increments (or post-decrements) return the old value before incrementing or decrementing, hence the name post-increment:

Instances

// Links to Github file Vault.sol:L443 VaultFactory.sol:L195

Actual codes

src/Vault.sol:443:        for (uint256 i = 0; i < epochsLength(); i++) {
src/VaultFactory.sol:195:        marketIndex += 1;

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

Using > 0 uses slightly more gas than using != 0. Use != 0 when comparing uint variables to zero, which cannot hold values below zero When dealing with unsigned integer types, comparisons with != 0 are cheaper then with > 0. This change saves 6 gas per instance Incidentally, after version 0.8.12, this optimization doesn’t work You should change from > 0 to !=0.

Instances

// Links to Github file Vault.sol:L187 PegOracle.sol:L98 PegOracle.sol:L121 StakingRewards.sol:L119

Actual codes

src/Vault.sol:187:        require(msg.value > 0, "ZeroValue");
src/oracles/PegOracle.sol:98:        require(price1 > 0, "Chainlink price <= 0");
src/oracles/PegOracle.sol:121:        require(price2 > 0, "Chainlink price <= 0");
src/rewards/StakingRewards.sol:119:        require(amount > 0, "Cannot withdraw 0");

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4. Variables: No need to explicitly initialize variables with default values

If a variable is not set/initialized, it is assumed to have the default value (0 for uint, false for bool, address(0) for address…). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

We can use uint number; instead of uint number = 0;

Instances:

// Links to github files StakingRewards.sol:L36

Actual Codes Used:

src/rewards/StakingRewards.sol:36:    uint256 public periodFinish = 0;

Recommended Mitigation Steps:

I suggest removing explicit initializations for default values.

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5.Use Custom Errors instead of Revert Strings to save Gas

Custom errors from Solidity 0.8.4 are cheaper than revert strings (cheaper deployment cost and runtime cost when the revert condition is met)

Source Custom Errors in Solidity:

Starting from Solidity v0.8.4, there is a convenient and gas-efficient way to explain to users why an operation failed through the use of custom errors. Until now, you could already use strings to give more information about failures (e.g., revert("Insufficient funds.");), but they are rather expensive, especially when it comes to deploy cost, and it is difficult to use dynamic information in them.

Custom errors are defined using the error statement, which can be used inside and outside of contracts (including interfaces and libraries).

Instances:

// Links to github files Vault.sol:L165 Vault.sol:L187 PegOracle.sol:L23 PegOracle.sol:L24 PegOracle.sol:L25 PegOracle.sol:L98 PegOracle.sol:L103 PegOracle.sol:L121 PegOracle.sol:L126 SemiFungibleVault.sol:L91 StakingRewards.sol:L96 StakingRewards.sol:L119

Actual Codes Used:

src/Vault.sol:165:        require((shares = previewDeposit(id, assets)) != 0, "ZeroValue");
src/Vault.sol:187:        require(msg.value > 0, "ZeroValue");
src/oracles/PegOracle.sol:23:        require(_oracle1 != address(0), "oracle1 cannot be the zero address");
src/oracles/PegOracle.sol:24:        require(_oracle2 != address(0), "oracle2 cannot be the zero address");
src/oracles/PegOracle.sol:25:        require(_oracle1 != _oracle2, "Cannot be same Oracle");
src/oracles/PegOracle.sol:98:        require(price1 > 0, "Chainlink price <= 0");
src/oracles/PegOracle.sol:103:        require(timeStamp1 != 0, "Timestamp == 0 !");
src/oracles/PegOracle.sol:121:        require(price2 > 0, "Chainlink price <= 0");
src/oracles/PegOracle.sol:126:        require(timeStamp2 != 0, "Timestamp == 0 !");
src/SemiFungibleVault.sol:91:        require((shares = previewDeposit(id, assets)) != 0, "ZERO_SHARES");
src/rewards/StakingRewards.sol:96:        require(amount != 0, "Cannot stake 0");
src/rewards/StakingRewards.sol:119:        require(amount > 0, "Cannot withdraw 0");

Recommended Mitigation Steps:

replace revert strings with custom errors.

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6. Use abi.encodePacked() not abi.encode()

Description

Changing abi.encode to abi.encodePacked can save gas. abi.encode pads extra null bytes at the end of the call data which is normally unnecessary. In general, abi.encodePacked is more gas-efficient.

Instances:

// Links to github files RewardsFactory.sol:L118 RewardsFactory.sol:L150 RewardsFactory.sol:L118 RewardsFactory.sol:L150

Actual Codes Used:

src/rewards/RewardsFactory.sol:118:        bytes32 hashedIndex = keccak256(abi.encode(_marketIndex, _epochEnd));
src/rewards/RewardsFactory.sol:150:        return keccak256(abi.encode(_index, _epoch));
src/rewards/RewardsFactory.sol:118:        bytes32 hashedIndex = keccak256(abi.encode(_marketIndex, _epochEnd));
src/rewards/RewardsFactory.sol:150:        return keccak256(abi.encode(_index, _epoch));

Recommended Mitigation Steps

You should change abi.encode to abi.encodePacked

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7. Compairing Boolean value to True or False

Comparing to a constant (true or false) is a bit more expensive than directly checking the returned boolean value. I suggest using if(directValue) instead of if(directValue == true) and if(!directValue) instead of if(directValue == false) here

Instances:

// Links to github files Vault.sol:L314 Controller.sol:L93 Controller.sol:L211 Vault.sol:L96 RewardsFactory.sol:L96

Actual Codes Used:

src/Vault.sol:314:        if(idExists[epochEnd] == true)
src/Controller.sol:93:        if(vault.idExists(epochEnd) == false)
src/Controller.sol:211:        if(insrVault.idExists(epochEnd) == false || riskVault.idExists(epochEnd) == false)
src/Vault.sol:96:        if((block.timestamp < id) && idDepegged[id] == false)
src/rewards/RewardsFactory.sol:96:        if(Vault(_insrToken).idExists(_epochEnd) == false || Vault(_riskToken).idExists(_epochEnd) == false)

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